FOUS30 KWBC 291555
QPFERD

Excessive Rainfall Discussion
NWS Weather Prediction Center College Park MD
1155 AM EDT Tue Apr 29 2025

Day 1
Valid 16Z Tue Apr 29 2025 - 12Z Wed Apr 30 2025

...THERE IS A MODERATE RISK OF EXCESSIVE RAINFALL FOR PORTIONS OF THE
SOUTHERN PLAINS...

...Southern Plains...

16Z UPDATE: No major change to the reasoning outlined below, but
there was an overall trend to shift risk areas southward a bit.
Although hi-res models (even the very recent 12Z runs) are
struggling to capture ongoing convection in the region, they all do consistently show organized convection this afternoon and evening
generating fairly strong cold pools, which in turn gradually pushes
the effective front south into N TX by this evening and overnight.
This is supported by RAP analysis showing higher DCAPE values
across portions of N TX, as well as the 12Z FWD sounding which=20
revealed a layer of fairly dry air just above the boundary layer.=20
Of the available hi-res models, recent runs of the RRFS seem to=20
best represent the forward propagating bow echo in S MO and=20
additional development in SW OK. Therefore, the tweaks to the=20
positioning of the risk areas leveraged the RRFS a bit more,=20
although some deference was given to other guidance sources as=20
well. Even models that aren't handling ongoing convection very well
still indicate the development of cold pools, and the tendency for
the axis of active convection to sink south with time. This lends=20
some confidence to the overall expectations described here. The
southward progression of the effective front seems to stall
overnight, which may lead to a rainfall max in N TX, or at least=20
very close to the Red River.

PREVIOUS DISCUSSION: A repetitive scheme of successive convective=20
outputs across portions of West TX through Oklahoma will result in=20 significant flash flooding for a large portion of the above areas.=20
The combination of several mid-level impulses ejecting northeast=20
within a large scale diffluent pattern will interact with a quasi-=20 stationary front aligned from the Western Rolling Plains of TX up=20
towards the Red River Basin mainly west of I-35. Favorable mid-=20
level ascent will allow for waves of convective initiation=20
beginning late-morning and afternoon Tuesday with a secondary pulse
around 00z Wednesday with a final pulse forecast after 06z as the=20
mean trough finally starts pivoting east out of the Southwestern=20
CONUS. Instability within the confines of West TX up to the Red=20
River will allow for rapid development of convective clusters with=20
some supercellular modes plausible prior to nightfall, eventually=20
merging into a more multi-cellular scheme with backbuilding favored
within the confines of the front denoted pretty well within the=20
theta_E gradient output in each deterministic. All CAMs are well=20
supportive of the 3-wave convective evolution with heavy rainfall=20
situated across the Southern High Plains near the eastern Permian=20
Basin with a general QPF maxima aligned southwest to northeast=20
across the northern extension of the Rolling Plains in TX, up=20
through the Red River and into the southern portion of the OKC=20
Metro. This area has been the benefactor of multiple convective=20
episodes already, leading to flash flooding within the corridor=20
extending from Lawton down to the Red River. This area will be the=20
most primed location for not only widespread flash flooding, but=20
significant life-threatening flash flood prospects due to the well=20
above normal soil moisture anomalies likely curbing any potential=20
for rainfall to soak into the top soil layer.

Latest 00z HREF probability fields are overwhelmingly indicative of
the threat with one of the more robust indications occurring
within the 6-hr FFG exceedance probability marker running between
70-90% across the area extending from Foard County in TX up to
western Cleveland County in OK. Neighborhood probabilities of >5"
total rainfall are running between 50-80% in the same location with

8" between 20-30% across Southwest OK between Lawton to the Red

River. Neighborhood probs for >3" are significant across much of OK
back into North TX with the southwest extension back into the
southeast corner of the LUB CWA. Considering the NASA SPoRT soil
moisture percentiles running between 70-99% for the 0-40cm layer
across the entire area above, the propensity for flooding, even in
rural zones will be higher than normal. Given expected rates
between 1-2"/hr during peak storm cycles and the expectation for

3" of rainfall...the threat will be of the higher magnitude in

terms of impact prospects. The previous MDT risk inherited was not
only maintained, but expanded a bit further southwest to align with
the higher probabilities with the neighborhood >5" potential and
the elevated HREF EAS >2" probabilities that have been depicted. A
high-end MDT risk is forecast across the Red River Basin west of
Wichita Falls up into the southern fringes of the OKC metro,
including the town of Norman. Lower end probabilities for flash
flooding will exist across areas of the eastern Permian Basin out
through the Concho Valley as well as across much of Oklahoma not
included in the MDT.

...Mississippi and Ohio Valleys...

16Z UPDATE: No major changes were made to the risk areas here.

PREVIOUS DISCUSSION: Mid-level impulses that eject out of the=20
Southern Plains will continue to press northeast towards the=20
Mississippi and Ohio Valleys with a progressive cold front moving=20
southeast out of the Midwest during the same time frame. Afternoon=20 destabilization coupled with the favorable addition of mid-level=20
forcing and surface frontogenesis will lead to scattered convective
pulses across the region with some organized elements focused=20
within the confines of the front and under the shortwave=20
propagation. Soils remain moist across much of the region extending
from MO through the Ohio River Basin with an eastern extension to=20
the Central Appalachians and Western PA Highlands. PWAT anomalies=20
on the order of +1 to as high as +2.5 deviations cements a=20
favorable deep moist environment conducive for heavy rainfall=20
prospects within any convective scheme. The greatest concentration=20
of heavy rain will likely be back over Southern and Central MO=20
towards the 3 river confluence zone near KY/MO/IN/IL. HREF probs=20
for >1" are very high (70-90+%) across much of the Mississippi and=20
Ohio Valley areas with >2" probs relatively high (50-70%) in-of the
Ohio River Basin over Southern IL through much of Eastern KY. The=20 combination of convection over areas that are still in recovery=20
from previous rainfall episodes and complex terrain will create a=20
threat for isolated to perhaps scattered flash flood instances over
a large area during the afternoon and evening hours Tuesday. A=20
SLGT risk remains firmly in place across much of MO along and south
of I-70 until the 3 river confluence zone referenced above. A MRGL
risk encompasses all other areas east through Western PA and even=20
the southwest corner of NY state.

Lamers/Kleebauer


Day 2
Valid 12Z Wed Apr 30 2025 - 12Z Thu May 01 2025

...THERE IS A MODERATE RISK OF EXCESSIVE RAINFALL FOR PORTIONS OF
THE ARKLATEX, EASTERN OKLAHOMA, AND WESTERN OZARKS...

The pattern remains very active as we move into Wednesday as the
mean trough slowly slips eastward with ample mid-level energy
accompanying, creating an environment favorable for organized
convective clusters through the entire D2 time frame. Rich Gulf air
will be pulled poleward ahead of the advancing trough with several
mid-level perturbations ejecting out of the ahead of the primary
shortwave trough. This in combination with sufficient buoyancy
across Central and East TX through the Mississippi Valley will
maintain a widespread convective zone of impact with strong, heavy
thunderstorm cores and clusters capable of producing prolific
rainfall totals.

Two primary periods of interest have become fairly well documented
within the recent deterministic cycles. The first is the
continuation of the convective complex that will develop overnight
Tuesday into Wednesday morning over the western Red River Basin and
slowly trudge eastward as it maneuvers in tandem with the primary
shortwave energy, and across the remaining theta_E gradient running
parallel to the river. 00z HREF on the back end of its run is
signaling some very impressive rainfall totals (2-5") within the
first 12 hr. period in the forecast cycle (12z Wed to 00z Thu)
across places along the Red River up through Central and Eastern OK
as the multi-cell cluster advances. Prob fields for >3" within
that first 12 hrs. are between 50-90% across south-central OK,
along and east of the I-35 corridor with 25-40% probs for even >5".
Considering this is only for the first 12 hrs., the probs are
pretty impressive and really highlight the threat on the initial
heavy QPF core.

The second period of interest will occur in the afternoon and
evening hrs. as diurnally driven convection will flare up over
Eastern TX within a broad moisture rich environment as NAEFS
anomalies continue to point to +2 to +3 deviations for PWATs
(1.5-2") situated over the area. LLJ introduction by early evening
will only exacerbate the potential with increasing low-level shear
capable of persisting updrafts and eventual cell clusters that will
originate from cells moving northeast within the mean flow. Several
mid-level perturbations will be in the vicinity across Northeast TX
to truly enhance and maintain convective cores such that it becomes
a fairly favorable prospect for heavy rainfall extending into the
Lower Mississippi Valley. Totals between 2-4" within an areal
expanse are forecast across the ArkLaTex up through Western AR to
just before the MO Ozarks. Locally higher totals will be possible
across that entire area given the favorable rates between 1-2.5"/hr
forecast currently within global deterministic. Pending outflow
propagation within the setup, heavier totals could advance further
east towards Central AR, but at this juncture, the primary area of
focus aligns over East TX up through Eastern OK and Western AR.
This correlates well with the theta_E ridge extension up through
the area where convective threats will be highest during peak
diurnal destabilization and beyond.

The previous MDT risk was maintained with a westward extension back
over portions of south-central OK down across the Red River into
TX. The MDT risk is NOT within the DFW metro, however it does lie
just north, so will have to monitor trends closely over the next
24-36 hrs. A broad SLGT risk extends south into East TX but well
north of the TX Gulf Coast.

Kleebauer

Day 3
Valid 12Z Thu May 01 2025 - 12Z Fri May 02 2025

...THERE IS A MARGINAL RISK OF EXCESSIVE RAINFALL FROM PORTIONS OF
THE LOWER MISSISSIPPI VALLEY UP THROUGH THE CENTRAL AND EASTERN
GREAT LAKES...

Numerous areas of thunderstorms will develop across the Mississippi
Valley through the east-central CONUS due to the progression of a
surface low out of the Southern Plains and attendant cold front
trailing the primary cyclone. Western Atlantic ridging will allow
for a continued advection of rich Gulf air into the Eastern U.S.
with a deep moist environment pretty much solidified from the Great
Lakes down to the Gulf coast. Area PWATs will run between 1.5-2.5
deviations above normal for much of the CONUS east of the
Mississippi, an environment very favorable for convective schemes
on the eastern flank of the surface low, as well as along and ahead
of the progressing cold front. Areal QPF within the ensemble means
are generally between 0.5 and 1" with some locally higher forecast
across the above area(s). Some of the deterministic output is of
course higher with some 2-4" maxima littered over the Southeast and
Ohio Valley where the convective scheme will be most prominent.
There's little agreement within the suite on exactly where the
heaviest precip will fall, but there's plenty of coverage where any
one spot could be the beneficiary of some heavy precip. At this
lead, would probably lean on the Tennessee Valley into the Southern
Ohio Valley to have the best potential due to a combo of antecedent
moist soils, as well as the greatest surface based ascent likely
within proxy to the advancing cold front. A broad MRGl risk exists
over parts of the Lower Mississippi up through the Central and
Eastern Great Lakes with the furthest east expansion over Western
NY state down to the Central Appalachians.

Kleebauer


Day 1 threat area: https://urldefense.com/v3/__https://www.wpc.ncep.noaa.gov/qpf/94epoints.txt= __;!!DZ3fjg!7tQ3PjlLi7vcDP-2JEbwn4tmrucmzdQMgvz7SmBuXkGrbgdP3Owj4pvrvdsNCFI= rjm1qkrjCYlLanOITNm-okHMigN4$=20
Day 2 threat area: https://urldefense.com/v3/__https://www.wpc.ncep.noaa.gov/qpf/98epoints.txt= __;!!DZ3fjg!7tQ3PjlLi7vcDP-2JEbwn4tmrucmzdQMgvz7SmBuXkGrbgdP3Owj4pvrvdsNCFI= rjm1qkrjCYlLanOITNm-oMKLuUNM$=20
Day 3 threat area: https://urldefense.com/v3/__https://www.wpc.ncep.noaa.gov/qpf/99epoints.txt= __;!!DZ3fjg!7tQ3PjlLi7vcDP-2JEbwn4tmrucmzdQMgvz7SmBuXkGrbgdP3Owj4pvrvdsNCFI= rjm1qkrjCYlLanOITNm-oB_mWhUw$=20

=3D =3D =3D
To unsubscribe from WX-STORM and you already have a login, go to https://lists.illinois.edu and use the "Unsubscribe" link. Otherwise email Chris Novy at cnovy@cox.net and ask to be removed from WX-STORM.

--- SBBSecho 3.20-Linux
* Origin: capitolcityonline.net * Telnet/SSH:2022/HTTP (1:2320/105)

FOUS30 KWBC 292021
QPFERD

Excessive Rainfall Discussion
NWS Weather Prediction Center College Park MD
421 PM EDT Tue Apr 29 2025

Day 1
Valid 16Z Tue Apr 29 2025 - 12Z Wed Apr 30 2025

...THERE IS A MODERATE RISK OF EXCESSIVE RAINFALL FOR PORTIONS OF THE
SOUTHERN PLAINS...

...Southern Plains...

16Z UPDATE: No major change to the reasoning outlined below, but
there was an overall trend to shift risk areas southward a bit.
Although hi-res models (even the very recent 12Z runs) are
struggling to capture ongoing convection in the region, they all do consistently show organized convection this afternoon and evening
generating fairly strong cold pools, which in turn gradually pushes
the effective front south into N TX by this evening and overnight.
This is supported by RAP analysis showing higher DCAPE values
across portions of N TX, as well as the 12Z FWD sounding which
revealed a layer of fairly dry air just above the boundary layer.
Of the available hi-res models, recent runs of the RRFS seem to
best represent the forward propagating bow echo in S MO and
additional development in SW OK. Therefore, the tweaks to the
positioning of the risk areas leveraged the RRFS a bit more,
although some deference was given to other guidance sources as
well. Even models that aren't handling ongoing convection very well
still indicate the development of cold pools, and the tendency for
the axis of active convection to sink south with time. This lends
some confidence to the overall expectations described here. The
southward progression of the effective front seems to stall
overnight, which may lead to a rainfall max in N TX, or at least
very close to the Red River.

PREVIOUS DISCUSSION: A repetitive scheme of successive convective
outputs across portions of West TX through Oklahoma will result in
significant flash flooding for a large portion of the above areas.
The combination of several mid-level impulses ejecting northeast
within a large scale diffluent pattern will interact with a quasi-
stationary front aligned from the Western Rolling Plains of TX up
towards the Red River Basin mainly west of I-35. Favorable mid-
level ascent will allow for waves of convective initiation
beginning late-morning and afternoon Tuesday with a secondary pulse
around 00z Wednesday with a final pulse forecast after 06z as the
mean trough finally starts pivoting east out of the Southwestern
CONUS. Instability within the confines of West TX up to the Red
River will allow for rapid development of convective clusters with
some supercellular modes plausible prior to nightfall, eventually
merging into a more multi-cellular scheme with backbuilding favored
within the confines of the front denoted pretty well within the
theta_E gradient output in each deterministic. All CAMs are well
supportive of the 3-wave convective evolution with heavy rainfall
situated across the Southern High Plains near the eastern Permian
Basin with a general QPF maxima aligned southwest to northeast
across the northern extension of the Rolling Plains in TX, up
through the Red River and into the southern portion of the OKC
Metro. This area has been the benefactor of multiple convective
episodes already, leading to flash flooding within the corridor
extending from Lawton down to the Red River. This area will be the
most primed location for not only widespread flash flooding, but
significant life-threatening flash flood prospects due to the well
above normal soil moisture anomalies likely curbing any potential
for rainfall to soak into the top soil layer.

Latest 00z HREF probability fields are overwhelmingly indicative of
the threat with one of the more robust indications occurring
within the 6-hr FFG exceedance probability marker running between
70-90% across the area extending from Foard County in TX up to
western Cleveland County in OK. Neighborhood probabilities of >5"
total rainfall are running between 50-80% in the same location with

8" between 20-30% across Southwest OK between Lawton to the Red

River. Neighborhood probs for >3" are significant across much of OK
back into North TX with the southwest extension back into the
southeast corner of the LUB CWA. Considering the NASA SPoRT soil
moisture percentiles running between 70-99% for the 0-40cm layer
across the entire area above, the propensity for flooding, even in
rural zones will be higher than normal. Given expected rates
between 1-2"/hr during peak storm cycles and the expectation for

3" of rainfall...the threat will be of the higher magnitude in

terms of impact prospects. The previous MDT risk inherited was not
only maintained, but expanded a bit further southwest to align with
the higher probabilities with the neighborhood >5" potential and
the elevated HREF EAS >2" probabilities that have been depicted. A
high-end MDT risk is forecast across the Red River Basin west of
Wichita Falls up into the southern fringes of the OKC metro,
including the town of Norman. Lower end probabilities for flash
flooding will exist across areas of the eastern Permian Basin out
through the Concho Valley as well as across much of Oklahoma not
included in the MDT.

...Mississippi and Ohio Valleys...

16Z UPDATE: No major changes were made to the risk areas here.

PREVIOUS DISCUSSION: Mid-level impulses that eject out of the
Southern Plains will continue to press northeast towards the
Mississippi and Ohio Valleys with a progressive cold front moving
southeast out of the Midwest during the same time frame. Afternoon destabilization coupled with the favorable addition of mid-level
forcing and surface frontogenesis will lead to scattered convective
pulses across the region with some organized elements focused
within the confines of the front and under the shortwave
propagation. Soils remain moist across much of the region extending
from MO through the Ohio River Basin with an eastern extension to
the Central Appalachians and Western PA Highlands. PWAT anomalies
on the order of +1 to as high as +2.5 deviations cements a
favorable deep moist environment conducive for heavy rainfall
prospects within any convective scheme. The greatest concentration
of heavy rain will likely be back over Southern and Central MO
towards the 3 river confluence zone near KY/MO/IN/IL. HREF probs
for >1" are very high (70-90+%) across much of the Mississippi and
Ohio Valley areas with >2" probs relatively high (50-70%) in-of the
Ohio River Basin over Southern IL through much of Eastern KY. The
combination of convection over areas that are still in recovery
from previous rainfall episodes and complex terrain will create a
threat for isolated to perhaps scattered flash flood instances over
a large area during the afternoon and evening hours Tuesday. A
SLGT risk remains firmly in place across much of MO along and south
of I-70 until the 3 river confluence zone referenced above. A MRGL
risk encompasses all other areas east through Western PA and even
the southwest corner of NY state.

Lamers/Kleebauer


Day 2
Valid 12Z Wed Apr 30 2025 - 12Z Thu May 01 2025

...THERE IS A MODERATE RISK OF EXCESSIVE RAINFALL FOR PORTIONS OF
SOUTH-CENTRAL AND SOUTHEAST OKLAHOMA, NORTH TEXAS, AND WESTERN
ARKANSAS...

The primary change for this updated ERO for Wednesday was to
recenter the Moderate Risk further south (approx. 50 mi). This was
due to a corresponding shift in guidance, especially hi-res
guidance, but also the UKMET, CMC, and ECMWF AIFS. It also fits
with the updated expectations for the current Day 1 period, as
guidance has signaled the potential for relatively strong cold
pools reinforcing the effective front and gradually pushing it
further south. This would center it more squarely near the Red
River (OK-TX border region) or perhaps fully into N TX. There is
still some uncertainty associated with the exact convective
evolution over the 12-18 hours immediately prior to the start of
the Day 2 period, so the Moderate Risk and Slight Risk were kept
fairly broad to account for different scenarios. Nevertheless,
there was a clear enough shift in the guidance to warrant an
adjustment in the overall risk contours.

A significant flash flooding event could be ongoing at the start of
the period (~12Z Wednesday) over western North Texas and/or south-
central and southwest Oklahoma. Late tonight the southward drift of
the effective front and the associated zone of active convection
may begin to slow or stall as the low-level jet (LLJ) begins to=20
ramp up considerably over Texas. Where the nose of the LLJ sets up
relative to ongoing convection will go a long way to determining
the primary area of concern for Wednesday. Most hi-res models show
the convective cluster(s) propagating east through the morning
toward AR and N LA, with renewed development upstream over N TX by
the afternoon and another training and backbuilding configuration.

This same guidance generally supports the idea of a 24-hour
rainfall maximum in excess of 7 inches somewhere in the new
Moderate Risk area, but there is lingering uncertainty as to
precisely where that will occur. Although the probability is
currently highest in the vicinity of the Red River near where SE OK
borders N TX, it's conceivable it could occur closer to or inside
the DFW metro area. The metro area is now fully in the Moderate
Risk area with this latest update.

Some significant flash flooding will be possible as much of the
rain will likely fall in 6-12 hours and the high end amounts
produced by some of the guidance would approach or exceed a 100
year ARI for those durations. Neighborhood probabilities of
100 year ARI exceedance are not particularly high, reflecting both
the uncertainty of the exact placement of the heaviest amounts, and
that amounts well in excess of those thresholds are not currently
supported by guidance. Significant and life-threatening flash=20
flooding would be most likely in two scenarios:=20

(1) In western North Texas or south-central Oklahoma at the=20
beginning of the period, as a continuation from the previous night.
These areas have been quite wet over the past week or so, so there
is existing vulnerability to extreme rainfall. (This is more
likely.)

(2) In the Dallas-Ft. Worth metro area, as the rainfall in question
would cause serious issues in a highly urbanized area. (This is
also possible, but not certain, and highly dependent on the exact
convective evolution.)

Further north, a broad Marginal and Slight Risk area was maintained
for the Mid Mississippi Valley and Central Plains. There is some
signal for organized convection and localized heavy rainfall,
including a scattering of low probabilities of FFG exceedance, but
confidence in any specific scenario is lacking.

Lamers

Day 3
Valid 12Z Thu May 01 2025 - 12Z Fri May 02 2025

...THERE IS A MARGINAL RISK OF EXCESSIVE RAINFALL OVER A BROAD AREA
FROM THE GREAT LAKES TO MID MISSISSIPPI VALLEY TO WESTERN GULF
COAST...

An expansive plume of instability is expected to support scattered
to numerous areas of thunderstorms during the day 3 period ahead of
a surface low and trailing cold front. Machine learning
probabilities from Colorado State support the idea of a broad
Marginal Risk; this is what was inherited and it was generally
maintained. The biggest change was to extend the area southwest
through portions of Louisiana and south and southeast Texas.
Confidence in specifics is low, and the overall flash flood threat
should be limited by the fairly progressive nature of the
convection. Precipitable water values are more anomalous in the
Great Lakes region (above the 90th percentile; above 1.3 inches),
but that is also where thunderstorms should be moving the fastest.
Meanwhile, available moisture will be less anomalous further south,
in TX and LA, but thunderstorms will be moving slower. Therefore,
heavy rainfall ingredients will generally be offset across the
whole region. Hi-res models that extend out beyond 48 hours show
more significant localized rainfall maxima in TX and LA, which
makes sense given stronger instability and slower overall storm
motions. This may be where a targeted upgrade to a Slight Risk is
eventually needed.

Lamers


Day 1 threat area: https://urldefense.com/v3/__https://www.wpc.ncep.noaa.gov/qpf/94epoints.txt= __;!!DZ3fjg!634Zb9891iMIpx13G31Ih9Q6SwdAo3JuS6R8-hUgWsJbS_Mxerk-c_1Pqs-SOAH= hdH-pxBTRP-Ct8xew5hpAbZzAmlA$=20
Day 2 threat area: https://urldefense.com/v3/__https://www.wpc.ncep.noaa.gov/qpf/98epoints.txt= __;!!DZ3fjg!634Zb9891iMIpx13G31Ih9Q6SwdAo3JuS6R8-hUgWsJbS_Mxerk-c_1Pqs-SOAH= hdH-pxBTRP-Ct8xew5hpApviFtvA$=20
Day 3 threat area: https://urldefense.com/v3/__https://www.wpc.ncep.noaa.gov/qpf/99epoints.txt= __;!!DZ3fjg!634Zb9891iMIpx13G31Ih9Q6SwdAo3JuS6R8-hUgWsJbS_Mxerk-c_1Pqs-SOAH= hdH-pxBTRP-Ct8xew5hpAB3dZ2zM$=20

=3D =3D =3D
To unsubscribe from WX-STORM and you already have a login, go to https://lists.illinois.edu and use the "Unsubscribe" link. Otherwise email Chris Novy at cnovy@cox.net and ask to be removed from WX-STORM.

--- SBBSecho 3.20-Linux
* Origin: capitolcityonline.net * Telnet/SSH:2022/HTTP (1:2320/105)

FOUS30 KWBC 300100
QPFERD

Excessive Rainfall Discussion
NWS Weather Prediction Center College Park MD
900 PM EDT Tue Apr 29 2025

Day 1
Valid 01Z Wed Apr 30 2025 - 12Z Wed Apr 30 2025

...THERE IS A MODERATE RISK OF EXCESSIVE RAINFALL FOR PORTIONS OF THE
SOUTHERN PLAINS...


...Southern Plains to the Mid Mississippi Valley...
01Z Update...

Continued the southern adjustment, especially on the northern edge,
of the outlook areas extending from western Texas northeastward
across Oklahoma. Recent runs of the HRRR, as well as the 18Z HREF,
indicate multiple convective rounds training northeastward across
the region, producing several inches of rain, with numerous flash=20
floods likely across portions of the region. The latest guidance=20
shows the greatest threat extending from Northwest Texas across the
Wichita Falls area into southwestern and south-central Oklahoma --
brushing the southern extent of the OKC metro. Deterministic runs=20
of the HRRR show accumulations of 7+ inches, while the HREF shows=20
high neighborhood probabilities for accumulations of 5 inches or=20
more through the overnight across this region. The Slight and=20
Moderate Risk areas were shifted a bit farther south across the=20
southern Texas Panhandle and western Oklahoma, where limited=20
instability in the most recent analysis supports guidance=20
indicating a lesser threat for heavy rainfall rates and flash=20
flooding.

Further to the east, pulled the Marginal and the Slight Risk areas
back west of the Mississippi. Relatively drier and more stable air
is expected to persist until showers and storms now developing=20
back to the southwest spread into the region late in the period,=20
with the general model consensus showing relatively lighter amounts
and a lesser flooding threat.

...Ohio Valley to the Central Appalachians...
01Z Update...

In addition to brief heavy downpours across sensitive areas, some=20
training along the southwest flank of the storms currently moving=20
across the region may raise the threat for locally heavy rains and=20
flash flooding. But overall, storms are expected to move
progressively across the area, limiting the potential for
widespread heavy rainfall and flash flooding concerns.=20

Pereira

Day 2
Valid 12Z Wed Apr 30 2025 - 12Z Thu May 01 2025

...THERE IS A MODERATE RISK OF EXCESSIVE RAINFALL FOR PORTIONS OF
SOUTH-CENTRAL AND SOUTHEAST OKLAHOMA, NORTH TEXAS, AND WESTERN
ARKANSAS...

The primary change for this updated ERO for Wednesday was to
recenter the Moderate Risk further south (approx. 50 mi). This was
due to a corresponding shift in guidance, especially hi-res
guidance, but also the UKMET, CMC, and ECMWF AIFS. It also fits
with the updated expectations for the current Day 1 period, as
guidance has signaled the potential for relatively strong cold
pools reinforcing the effective front and gradually pushing it
further south. This would center it more squarely near the Red
River (OK-TX border region) or perhaps fully into N TX. There is
still some uncertainty associated with the exact convective
evolution over the 12-18 hours immediately prior to the start of
the Day 2 period, so the Moderate Risk and Slight Risk were kept
fairly broad to account for different scenarios. Nevertheless,
there was a clear enough shift in the guidance to warrant an
adjustment in the overall risk contours.

A significant flash flooding event could be ongoing at the start of
the period (~12Z Wednesday) over western North Texas and/or south-
central and southwest Oklahoma. Late tonight the southward drift of
the effective front and the associated zone of active convection
may begin to slow or stall as the low-level jet (LLJ) begins to
ramp up considerably over Texas. Where the nose of the LLJ sets up
relative to ongoing convection will go a long way to determining
the primary area of concern for Wednesday. Most hi-res models show
the convective cluster(s) propagating east through the morning
toward AR and N LA, with renewed development upstream over N TX by
the afternoon and another training and backbuilding configuration.

This same guidance generally supports the idea of a 24-hour
rainfall maximum in excess of 7 inches somewhere in the new
Moderate Risk area, but there is lingering uncertainty as to
precisely where that will occur. Although the probability is
currently highest in the vicinity of the Red River near where SE OK
borders N TX, it's conceivable it could occur closer to or inside
the DFW metro area. The metro area is now fully in the Moderate
Risk area with this latest update.

Some significant flash flooding will be possible as much of the
rain will likely fall in 6-12 hours and the high end amounts
produced by some of the guidance would approach or exceed a 100
year ARI for those durations. Neighborhood probabilities of
100 year ARI exceedance are not particularly high, reflecting both
the uncertainty of the exact placement of the heaviest amounts, and
that amounts well in excess of those thresholds are not currently
supported by guidance. Significant and life-threatening flash
flooding would be most likely in two scenarios:

(1) In western North Texas or south-central Oklahoma at the
beginning of the period, as a continuation from the previous night.
These areas have been quite wet over the past week or so, so there
is existing vulnerability to extreme rainfall. (This is more
likely.)

(2) In the Dallas-Ft. Worth metro area, as the rainfall in question
would cause serious issues in a highly urbanized area. (This is
also possible, but not certain, and highly dependent on the exact
convective evolution.)

Further north, a broad Marginal and Slight Risk area was maintained
for the Mid Mississippi Valley and Central Plains. There is some
signal for organized convection and localized heavy rainfall,
including a scattering of low probabilities of FFG exceedance, but
confidence in any specific scenario is lacking.

Lamers

Day 3
Valid 12Z Thu May 01 2025 - 12Z Fri May 02 2025

...THERE IS A MARGINAL RISK OF EXCESSIVE RAINFALL OVER A BROAD AREA
FROM THE GREAT LAKES TO MID MISSISSIPPI VALLEY TO WESTERN GULF
COAST...

An expansive plume of instability is expected to support scattered
to numerous areas of thunderstorms during the day 3 period ahead of
a surface low and trailing cold front. Machine learning
probabilities from Colorado State support the idea of a broad
Marginal Risk; this is what was inherited and it was generally
maintained. The biggest change was to extend the area southwest
through portions of Louisiana and south and southeast Texas.
Confidence in specifics is low, and the overall flash flood threat
should be limited by the fairly progressive nature of the
convection. Precipitable water values are more anomalous in the
Great Lakes region (above the 90th percentile; above 1.3 inches),
but that is also where thunderstorms should be moving the fastest.
Meanwhile, available moisture will be less anomalous further south,
in TX and LA, but thunderstorms will be moving slower. Therefore,
heavy rainfall ingredients will generally be offset across the
whole region. Hi-res models that extend out beyond 48 hours show
more significant localized rainfall maxima in TX and LA, which
makes sense given stronger instability and slower overall storm
motions. This may be where a targeted upgrade to a Slight Risk is
eventually needed.

Lamers


Day 1 threat area: https://urldefense.com/v3/__https://www.wpc.ncep.noaa.gov/qpf/94epoints.txt= __;!!DZ3fjg!-9whLZQzN1K2RbQb4fPLyt4fk4hbu55oU5N2bNKsgCQP8mLvWERMZ9Vl-8Gv8Tn= G3WleDjuE62VsInKesiH6UDexBMw$=20
Day 2 threat area: https://urldefense.com/v3/__https://www.wpc.ncep.noaa.gov/qpf/98epoints.txt= __;!!DZ3fjg!-9whLZQzN1K2RbQb4fPLyt4fk4hbu55oU5N2bNKsgCQP8mLvWERMZ9Vl-8Gv8Tn= G3WleDjuE62VsInKesiH6P7qS7lo$=20
Day 3 threat area: https://urldefense.com/v3/__https://www.wpc.ncep.noaa.gov/qpf/99epoints.txt= __;!!DZ3fjg!-9whLZQzN1K2RbQb4fPLyt4fk4hbu55oU5N2bNKsgCQP8mLvWERMZ9Vl-8Gv8Tn= G3WleDjuE62VsInKesiH6jiK5zZw$=20

=3D =3D =3D
To unsubscribe from WX-STORM and you already have a login, go to https://lists.illinois.edu and use the "Unsubscribe" link. Otherwise email Chris Novy at cnovy@cox.net and ask to be removed from WX-STORM.

--- SBBSecho 3.20-Linux
* Origin: capitolcityonline.net * Telnet/SSH:2022/HTTP (1:2320/105)

FOUS30 KWBC 300733
QPFERD

Excessive Rainfall Discussion
NWS Weather Prediction Center College Park MD
333 AM EDT Wed Apr 30 2025

Day 1
Valid 12Z Wed Apr 30 2025 - 12Z Thu May 01 2025

...THERE IS A MODERATE RISK OF EXCESSIVE RAINFALL FOR PORTIONS OF
SOUTH-CENTRAL AND SOUTHEAST OKLAHOMA, NORTH TEXAS, AND WESTERN
ARKANSAS...

The overall synoptic pattern remains unchanged in terms of the
general longwave progression as an amplified mid-level trough
begins to open up overnight and kick eastward with a strong
vorticity maxima riding the base of the mean trough. Ample mid-
level ascent within a fairly moisture rich environment thanks to
coupled LLJ advection and strong 700-500mb moisture feed from the
above trough will lead to a period of prolonged convective
maintenance and initiation over the course of Wednesday into early
Thursday morning. A strong mid-level shortwave ejection is
currently migrating eastward out of NM with WV and IR satellite
already showing instances of cooling cloud tops marking the sign of
the final wave of convective initiation off the Caprock and
adjacent Permian Basin. This expanse of convective development will
usher east-northeastward within the mean flow, also anchoring to
the quasi-stationary boundary positioned back across the Permian
Basin through the Western Rolling Plains of TX. Heavy thunderstorms=20
prior have led to a swath of very low FFG's in their wake creating
an antecedent soil moisture condition incapable of taking on much
more rainfall before causing flash flooding, some significant in
nature given the ongoing issues near the Red River.=20

As the shortwave trough migrates through North TX and the Red River
Basin, cold pool convergence during nocturnal convective cycles
will lead to a conglomeration of heavy thunderstorms extending from
Central OK down through North TX, advancing eastward within the
confines of the stationary front. By 12z Wednesday, rainfall rates
between 1-2"/hr at peak intensity will encompass a pretty large
area with the western extent of the precip footprint likely
overlapping areas that were hit recently this evening. This area
will represent the western extent of the inherited MDT risk as
outlined as 00z CAMs have come into relative agreement on the
timing of the convective cluster moving through the region in the
initial stages of the forecast cycle. The primary energy will
continue to traverse eastward with the afternoon period likely to
see the shortwave axis bisecting Southeast OK between the 18-00z
time frame. This is where the next round of convective impacts will transpire.=20

As of the latest ensemble bias corrected mean and HREF blended mean
output, the heaviest precip has shaded a bit further south compared
to run-to-run consistency, a tendency typically seen in these
setups due to the greater instability located further south, as
well as cold pool progression tending to move southeastward within
the theta_E gradient pattern(s). This is no different with a strong
signal for 2-4" areal averages located over Northeast TX with the
2" mean now even southeast of the DFW metro. 3-5" is the average
over the ArkLaTex bisecting the Red River Basin between OK/TX/LA,
something that has remained steady despite the overall shift
further south in the heavier convective forecast. This is the most
likely location for flash flood prospects, certifying the centroid
of the current MDT well-positioned and left untouched from previous forecast.=20

With the scope of the heavier precip now aligned a bit further
south to include the DFW metro and areas along I-20, the MDT was
pulled a bit further south to encompass the 00z HREF >5" neighborhood
probs of at least 30% or higher, with the general maxima located
along I-30 towards Texarkana. This correlates well with the
forecasted position of favorable PWAT anomalies +2 or better when
assessing the most recent NAEFS and ECENS outputs. Hourly rates
between 1-2"/hr will be most common at peak intensity according to
the HREF hourly prob fields with 1"/hr running between 50-90% at
any given time between 18-06z in the forecast across Northeast TX
up into Southeast OK and Western AR. 2"/hr probs are not as
prolific in the signal, but considering the sheared profile and
deep boundary layer moisture advection pattern, would not be
surprised to see some cells percolate >2"/hr given the expected
environment.

The DFW metro is one of the areas of focus due to the risk of flash
flooding being higher with the urbanization factors at hand. There
are some CAMs hinting at significant totals within the metro
proper, but some are just missing the population center to the
north and east during the overall evolution. Considering the
environmental conditioning and the nature of the heavy precip being
within a short proxy, regardless of eventual outcome the MDT risk
was sufficient to cover for the threat. HREF EAS prob fields for at
least 2" running between 30-50%, west to east across the metroplex
is a pretty good signal for the threat and that signal only
improves as you move eastward through the I-20/30 zones.=20

There is a large SLGT risk that encompasses much of the Lower
Mississippi Valley and basically the rest of the northeastern
quadrant of TX up through Central OK. Scattered to bordering
widespread convection will be forecast from the Ozarks and points
southwest with some locally enhanced cores likely to spur some
flash flood potential with low to medium grade probabilities
suggest. There's some question on the exact location of these more
isolated heavy cells, however there's some indication a secondary
maxima could be within south-central TX near the eastern flank of
the terrain east of I-35, or across MO where diffluent upper flow
will be positioned well to enhance regional convective coverage
within a fairly moist environment as the anomalous PWATs funnel
poleward.

Kleebauer


Day 2
Valid 12Z Thu May 01 2025 - 12Z Fri May 02 2025

...THERE IS A MARGINAL RISK OF EXCESSIVE RAINFALL OVER A BROAD=20
AREA FROM THE GREAT LAKES TO MID MISSISSIPPI VALLEY TO WESTERN GULF
COAST...

Surface cyclogenesis across the Southern Plains will lead to a
steady low progression to the northeast up through the Mississippi
Valley into the Great Lakes towards the end of the forecast cycle.
A cold front will trail the vacating low allowing for some frontal
convergence to occur across the above areas with the greatest=20
convective coverage likely to be within the warm sector of the Ohio
and Tennessee Valley into the southern Great Lakes. PWAT anomalies
between +2 and +3 deviations will be present for much of the CONUS
situated east of the Mississippi lending to a fairly rich=20
environment conducive for moist convective cores from the Gulf=20
coast up to the Great Lakes region. The reasoning for the heavier=20
convective threat north is the added sheared profiles within the=20
bounds of the warm sector creating better mesocyclone maturity and=20
stronger storms. All this to say....heavy rain prospects for longer
periods more likely within the zone encompassing the Tennessee and
Ohio Valleys. Current forecast totals region-wide over the=20
Southeast up into the Ohio Valley are pretty consistent with an=20
areal average between 0.5 to 1" with some locally enhanced totals=20
reaching upwards of 2-2.5" in the hardest hit locations. Given=20
rainfall rates peaking between 1-1.5"/hr when assessing the=20
probabilistic output of both the NBM and 00z HREF, there's a cap on
the higher end potential of any flash flood scenario leaving this=20
overall threat in the broad MRGL risk coverage, as inherited.=20

There is another area of interest down across the Rio Grande
extending from the Big Bend down to about Laredo for tomorrow
evening as a shortwave perturbation ejects east off of Coahuila=20
with some convection spawning over the Serranias del Burro. Some of
the CAMs are pretty significant in the overall convective
development, but much of the CAMs reach the end of their runs prior
to the activity making its way towards the Rio Grande Valley. Other deterministic and ensemble bias corrected means tell the story in
full with some respectable QPF outputs within the above bounds
leading to potentially some localized flooding within some of the
urbanized zones between Del Rio down to Laredo. Considering the
environment to be favorable and this scenario having a long history
of potential, opted to keep the MRGL risk from previous forecast
issuance to outline the threat for a quick 1-3" of rainfall with
locally higher amounts plausible pending cold pool convergence
evolutions.=20

Kleebauer


Day 3
Valid 12Z Fri May 02 2025 - 12Z Sat May 03 2025

...THERE IS A SLIGHT RISK OF EXCESSIVE RAINFALL ACROSS MUCH OF
CENTRAL TEXAS...

A cold front progression stemming from a trailing cold front and
pressing surface high over the Northern Plains will lead to
significant low-level convergence regime over Central TX by Friday
afternoon. Return flow around the western flank of a broad surface
ridge positioned over the Western Atlantic will reach back towards
the southern half of TX leading to a convergent pattern in
conjunction with slow-moving cold front moving north to south.
Models have been steadily increasing precip coverage within the
confines of the boundary once it makes headway into the Hill
Country of the Lone Star State by late-Friday morning, carrying
through the rest of the period as the front encounters higher
theta_E airmass within the western periphery of that surface ridge.
PWATs between +1 and +2 deviations will be present once the front
makes its presence across the region, a sufficient environment for
deep moist convective development along and ahead of the boundary
as it slowly migrates south. Ensemble means have upped precip
output in recent runs with a solid 1-2" areal average now
encompassing a large portion of the state from the Stockton
Plateau, east through Hill Country, the I-35 corridor, all the way
back towards the Piney Woods area of East TX. Favorable environment
with likely training echoes in proxy to the cold front will
generate locally enhanced QPF maxima, especially within the bounds
of the terrain where an added weak upslope component could yield
greatest results (3+" totals). The convergent pattern can be seen
as far east as the Southeastern CONUS, but the greatest surface
frontogenesis signal is situated back over the Southern Plains,
south of I-20.=20

A SLGT risk was added across the above area with a broad MRGL
encompassing the higher risk as scattered convection will still be
present up towards I-20 extending east through the Lower
Mississippi Valley up through Northern AL and Eastern TN. Will be
monitoring the setup closely as the setup will likely be most
prolific within one of the flashier areas of the country.=20

Kleebauer


Day 1 threat area: https://urldefense.com/v3/__https://www.wpc.ncep.noaa.gov/qpf/94epoints.txt= __;!!DZ3fjg!9dnw4QOmP0kxRSxS3tp5a_4PEkYyeWmg9-SchkFStpVdvOvqtjrOVSzD35lWtv0= 4Ih_D8WUu7PRxdrUUoJQOCiIi8j8$=20
Day 2 threat area: https://urldefense.com/v3/__https://www.wpc.ncep.noaa.gov/qpf/98epoints.txt= __;!!DZ3fjg!9dnw4QOmP0kxRSxS3tp5a_4PEkYyeWmg9-SchkFStpVdvOvqtjrOVSzD35lWtv0= 4Ih_D8WUu7PRxdrUUoJQOZP0l4uI$=20
Day 3 threat area: https://urldefense.com/v3/__https://www.wpc.ncep.noaa.gov/qpf/99epoints.txt= __;!!DZ3fjg!9dnw4QOmP0kxRSxS3tp5a_4PEkYyeWmg9-SchkFStpVdvOvqtjrOVSzD35lWtv0= 4Ih_D8WUu7PRxdrUUoJQOhfmWY_s$=20

=3D =3D =3D
To unsubscribe from WX-STORM and you already have a login, go to https://lists.illinois.edu and use the "Unsubscribe" link. Otherwise email Chris Novy at cnovy@cox.net and ask to be removed from WX-STORM.

--- SBBSecho 3.20-Linux
* Origin: capitolcityonline.net * Telnet/SSH:2022/HTTP (1:2320/105)

FOUS30 KWBC 301551
QPFERD

Excessive Rainfall Discussion
NWS Weather Prediction Center College Park MD
1151 AM EDT Wed Apr 30 2025

Day 1
Valid 16Z Wed Apr 30 2025 - 12Z Thu May 01 2025

...THERE IS A MODERATE RISK OF EXCESSIVE RAINFALL FOR PORTIONS OF
SOUTHEAST OKLAHOMA, NORTH TEXAS, AND WESTERN ARKANSAS...

The threat of significant flash flooding continues today, with the
focus increasingly shifting to portions of north Texas based on
observational trends and the latest 12Z hi-res model guidance.

A bowing convective line continues to advance eastward through
S OK, with a trailing line of convection extending into N TX on=20
the southern periphery of strong cold pool and mesohigh situated=20
over SC OK. Over the past couple hours, the convective line in N=20
TX has become increasingly oriented NE-SW, or even ENE-WSW; in=20
other words, more parallel to the mean flow vector. This has=20
increased the potential for training and backbuilding, especially=20
into the afternoon hours as the LLJ begins to weaken and low-level=20
winds start to veer to the southwest. For a more detailed mesoscale
analysis, please refer to MPD #202 issued at 14Z for this region.

The Moderate Risk area was maintained in SE OK and W AR, even
though confidence in flash flooding has decreased somewhat due to
the fairly steady forward progress of the bowing line, and how thin
the convective line has become. However, it was maintained out of
deference to continuity and the potential to reinvigorate the=20
convection in the next few hours with some clearing occurring ahead
of the line, which could increase rain rates again.

Greater concern now exists in N TX. The forward progression of the
line and associated cold pool in S OK and overall convective
evolution has led to far more west-east orientation to the
convective line in N TX than models had originally been
advertising. This certainly increases flash flood potential and
over the next few hours this places the Dallas-Ft. Worth metro area
squarely in the greatest risk. Hourly rainfall could exceed 2
inches per hour, with unobstructed inflow from a very moist and
unstable air mass (MLCAPE 1500-2000 j/kg with minimal CINH; PWs=20
1.6 to 1.8 inches per RAP analysis.) In an urban environment, this
could lead to significant and life-threatening flash flooding,
particularly if the rain rates are sustained for a couple hours,
which is a distinct possibility in this case.=20

As the afternoon and evening progress, the hi-res models do
indicate the potential for the southwestern periphery of the
convective line to continue to slow or stall. While they don't
necessarily agree on the specifics, many HREF members, as well as
the RRFS, indicate backbuilding and training convection could
become more likely in the corridor from Waco to Longview. This
seems to be well supported by observational trends, and in fact
many hi-res members are: (1) already not extending the convective=20
line far enough southwest based on current radar trends, and (2)
have the convective line oriented far too much in a N-S fashion.
Therefore, they may be underestimating rainfall potential a bit,
and also underselling the potential for a significant rainfall and
flash flood event further to the southwest. Probabilities and
associated risk categories were increased a bit down the I-35
corridor between DFW and AUS, and this will be monitored for
further updates based on observational trends. Rain rates in much
of C/N TX could reach or exceed 2 inches per hour given the=20
available instability and moisture.

The other biggest change for this outlook was to extend the Slight
Risk a bit further northeast through MO and into W IL based on more
elevated HREF probabilities of exceeding 1hr and 3hr flash flood
guidance and a fairly consistent signal in the guidance for a
corridor of enhanced rainfall associated with an MCV and
corresponding surface low.

Lamers


Day 2
Valid 12Z Thu May 01 2025 - 12Z Fri May 02 2025

...THERE IS A MARGINAL RISK OF EXCESSIVE RAINFALL OVER A BROAD
AREA FROM THE GREAT LAKES TO MID MISSISSIPPI VALLEY TO WESTERN GULF
COAST...

Surface cyclogenesis across the Southern Plains will lead to a
steady low progression to the northeast up through the Mississippi
Valley into the Great Lakes towards the end of the forecast cycle.
A cold front will trail the vacating low allowing for some frontal
convergence to occur across the above areas with the greatest
convective coverage likely to be within the warm sector of the Ohio
and Tennessee Valley into the southern Great Lakes. PWAT anomalies
between +2 and +3 deviations will be present for much of the CONUS
situated east of the Mississippi lending to a fairly rich
environment conducive for moist convective cores from the Gulf
coast up to the Great Lakes region. The reasoning for the heavier
convective threat north is the added sheared profiles within the
bounds of the warm sector creating better mesocyclone maturity and
stronger storms. All this to say....heavy rain prospects for longer
periods more likely within the zone encompassing the Tennessee and
Ohio Valleys. Current forecast totals region-wide over the
Southeast up into the Ohio Valley are pretty consistent with an
areal average between 0.5 to 1" with some locally enhanced totals
reaching upwards of 2-2.5" in the hardest hit locations. Given
rainfall rates peaking between 1-1.5"/hr when assessing the
probabilistic output of both the NBM and 00z HREF, there's a cap on
the higher end potential of any flash flood scenario leaving this
overall threat in the broad MRGL risk coverage, as inherited.

There is another area of interest down across the Rio Grande
extending from the Big Bend down to about Laredo for tomorrow
evening as a shortwave perturbation ejects east off of Coahuila
with some convection spawning over the Serranias del Burro. Some of
the CAMs are pretty significant in the overall convective
development, but much of the CAMs reach the end of their runs prior
to the activity making its way towards the Rio Grande Valley. Other deterministic and ensemble bias corrected means tell the story in
full with some respectable QPF outputs within the above bounds
leading to potentially some localized flooding within some of the
urbanized zones between Del Rio down to Laredo. Considering the
environment to be favorable and this scenario having a long history
of potential, opted to keep the MRGL risk from previous forecast
issuance to outline the threat for a quick 1-3" of rainfall with
locally higher amounts plausible pending cold pool convergence
evolutions.

Kleebauer


Day 3
Valid 12Z Fri May 02 2025 - 12Z Sat May 03 2025

...THERE IS A SLIGHT RISK OF EXCESSIVE RAINFALL ACROSS MUCH OF
CENTRAL TEXAS...

A cold front progression stemming from a trailing cold front and
pressing surface high over the Northern Plains will lead to
significant low-level convergence regime over Central TX by Friday
afternoon. Return flow around the western flank of a broad surface
ridge positioned over the Western Atlantic will reach back towards
the southern half of TX leading to a convergent pattern in
conjunction with slow-moving cold front moving north to south.
Models have been steadily increasing precip coverage within the
confines of the boundary once it makes headway into the Hill
Country of the Lone Star State by late-Friday morning, carrying
through the rest of the period as the front encounters higher
theta_E airmass within the western periphery of that surface ridge.
PWATs between +1 and +2 deviations will be present once the front
makes its presence across the region, a sufficient environment for
deep moist convective development along and ahead of the boundary
as it slowly migrates south. Ensemble means have upped precip
output in recent runs with a solid 1-2" areal average now
encompassing a large portion of the state from the Stockton
Plateau, east through Hill Country, the I-35 corridor, all the way
back towards the Piney Woods area of East TX. Favorable environment
with likely training echoes in proxy to the cold front will
generate locally enhanced QPF maxima, especially within the bounds
of the terrain where an added weak upslope component could yield
greatest results (3+" totals). The convergent pattern can be seen
as far east as the Southeastern CONUS, but the greatest surface
frontogenesis signal is situated back over the Southern Plains,
south of I-20.

A SLGT risk was added across the above area with a broad MRGL
encompassing the higher risk as scattered convection will still be
present up towards I-20 extending east through the Lower
Mississippi Valley up through Northern AL and Eastern TN. Will be
monitoring the setup closely as the setup will likely be most
prolific within one of the flashier areas of the country.

Kleebauer


Day 1 threat area: https://urldefense.com/v3/__https://www.wpc.ncep.noaa.gov/qpf/94epoints.txt= __;!!DZ3fjg!8JYv3_3vErz0562OCSAEyf0IRviJoNKVNSAOQ7-SPDNf-KLySIzJD7gIqnh1aUz= ihIjriYSQxTMaCJF4DosR2jry334$=20
Day 2 threat area: https://urldefense.com/v3/__https://www.wpc.ncep.noaa.gov/qpf/98epoints.txt= __;!!DZ3fjg!8JYv3_3vErz0562OCSAEyf0IRviJoNKVNSAOQ7-SPDNf-KLySIzJD7gIqnh1aUz= ihIjriYSQxTMaCJF4DosRbc3geoU$=20
Day 3 threat area: https://urldefense.com/v3/__https://www.wpc.ncep.noaa.gov/qpf/99epoints.txt= __;!!DZ3fjg!8JYv3_3vErz0562OCSAEyf0IRviJoNKVNSAOQ7-SPDNf-KLySIzJD7gIqnh1aUz= ihIjriYSQxTMaCJF4DosRPURawxg$=20

=3D =3D =3D
To unsubscribe from WX-STORM and you already have a login, go to https://lists.illinois.edu and use the "Unsubscribe" link. Otherwise email Chris Novy at cnovy@cox.net and ask to be removed from WX-STORM.

--- SBBSecho 3.20-Linux
* Origin: capitolcityonline.net * Telnet/SSH:2022/HTTP (1:2320/105)

FOUS30 KWBC 302017
QPFERD

Excessive Rainfall Discussion
NWS Weather Prediction Center College Park MD
417 PM EDT Wed Apr 30 2025

Day 1
Valid 16Z Wed Apr 30 2025 - 12Z Thu May 01 2025

...THERE IS A MODERATE RISK OF EXCESSIVE RAINFALL FOR PORTIONS OF
SOUTHEAST OKLAHOMA, NORTH TEXAS, AND WESTERN ARKANSAS...

The threat of significant flash flooding continues today, with the
focus increasingly shifting to portions of north Texas based on
observational trends and the latest 12Z hi-res model guidance.

A bowing convective line continues to advance eastward through
S OK, with a trailing line of convection extending into N TX on
the southern periphery of strong cold pool and mesohigh situated
over SC OK. Over the past couple hours, the convective line in N
TX has become increasingly oriented NE-SW, or even ENE-WSW; in
other words, more parallel to the mean flow vector. This has
increased the potential for training and backbuilding, especially
into the afternoon hours as the LLJ begins to weaken and low-level
winds start to veer to the southwest. For a more detailed mesoscale
analysis, please refer to MPD #202 issued at 14Z for this region.

The Moderate Risk area was maintained in SE OK and W AR, even
though confidence in flash flooding has decreased somewhat due to
the fairly steady forward progress of the bowing line, and how thin
the convective line has become. However, it was maintained out of
deference to continuity and the potential to reinvigorate the
convection in the next few hours with some clearing occurring ahead
of the line, which could increase rain rates again.

Greater concern now exists in N TX. The forward progression of the
line and associated cold pool in S OK and overall convective
evolution has led to far more west-east orientation to the
convective line in N TX than models had originally been
advertising. This certainly increases flash flood potential and
over the next few hours this places the Dallas-Ft. Worth metro area
squarely in the greatest risk. Hourly rainfall could exceed 2
inches per hour, with unobstructed inflow from a very moist and
unstable air mass (MLCAPE 1500-2000 j/kg with minimal CINH; PWs
1.6 to 1.8 inches per RAP analysis.) In an urban environment, this
could lead to significant and life-threatening flash flooding,
particularly if the rain rates are sustained for a couple hours,
which is a distinct possibility in this case.

As the afternoon and evening progress, the hi-res models do
indicate the potential for the southwestern periphery of the
convective line to continue to slow or stall. While they don't
necessarily agree on the specifics, many HREF members, as well as
the RRFS, indicate backbuilding and training convection could
become more likely in the corridor from Waco to Longview. This
seems to be well supported by observational trends, and in fact
many hi-res members are: (1) already not extending the convective
line far enough southwest based on current radar trends, and (2)
have the convective line oriented far too much in a N-S fashion.
Therefore, they may be underestimating rainfall potential a bit,
and also underselling the potential for a significant rainfall and
flash flood event further to the southwest. Probabilities and
associated risk categories were increased a bit down the I-35
corridor between DFW and AUS, and this will be monitored for
further updates based on observational trends. Rain rates in much
of C/N TX could reach or exceed 2 inches per hour given the
available instability and moisture.

The other biggest change for this outlook was to extend the Slight
Risk a bit further northeast through MO and into W IL based on more
elevated HREF probabilities of exceeding 1hr and 3hr flash flood
guidance and a fairly consistent signal in the guidance for a
corridor of enhanced rainfall associated with an MCV and
corresponding surface low.

Lamers


Day 2
Valid 12Z Thu May 01 2025 - 12Z Fri May 02 2025

...THERE IS A SLIGHT RISK OF EXCESSIVE RAINFALL IN SOUTHERN
OKLAHOMA, FAR NORTH TEXAS, AND FAR WESTERN ARKANSAS...

The most significant change for this outlook period was to
introduce a Slight Risk primarily over southern Oklahoma, where
previously the probabilities were below the Marginal Risk (5
percent) threshold. This was due to an emerging consensus in model
guidance that thunderstorms will blossom on Thursday Night ahead of
a digging shortwave in an area of relatively strong upper level
divergence. Although the mid levels will be drier than in recent
days, leading to lower PWs overall, strong instability will be in=20
place which should support organized convection with more intense=20
rain rates at times. A key uncertainty at the moment is the overall
structure of convective clusters and lines, and whether they will=20
be more progressive or include some training. However, the=20
potential for heavy rain rates in an area that has received a lot=20
of rainfall already in recent days does raise the risk of flash
flooding. Hourly rainfall on the order of 1-2 inches will be
possible in this environment, and in areas with already wet ground
conditions this would be more than sufficient to cause flash
flooding.

Elsewhere, the broad Marginal Risk that was already in place was
maintained with few changes. A broad plume of moderate to strong
instability will favor scattered lines and clusters of
thunderstorms in advance of a surface low and trailing cold front
with fairly high instantaneous rain rates. The key uncertainty
would be the persistence of those rain rates and the degree to
which any training could occur, but the overall environment with
PWs around 1.3 to 1.4 inches raises the probability high enough to
warrant the broad Marginal Risk. The only exception to the
continuation of the risk area was over much of IL, IN, and MI,
which should largely be behind the cold front by 18Z and so most of
the QPF on model guidance would be associated with post-frontal
showers that would tend to have lower rain rates overall.

Lamers


Day 3
Valid 12Z Fri May 02 2025 - 12Z Sat May 03 2025

...THERE IS A SLIGHT RISK OF EXCESSIVE RAINFALL ACROSS FROM THE
SOUTHERN PLAINS INTO THE LOWER MISSISSIPPI VALLEY...

A flash flood event may be ongoing at the beginning of the period,
with convection developing on Thursday Night in southern Oklahoma
and continuing into Friday morning. This may continue beyond 12Z
Friday (into this Day 3 period) in SE OK and AR in the region of
strong upper-level divergence. The existing Slight Risk over TX was
expanded northward to account for this scenario. Whether that round
of convection wanes due to more extensive cloud cover and limited
daytime heating, or progresses southeast and becomes reinvigorated
during the afternoon, the threat of heavy rainfall and flash
flooding should expand southeast on Friday into the Lower
Mississippi Valley (S AR, N LA, W MS) and much of C and E TX. This
would be via progression of the early round of storms, or
redevelopment in the afternoon and evening hours.=20

Strong instability will remain over much of the warm sector with=20
CAPE values potentially in excess of 3000 j/kg in some areas, and=20
PW values are expected to increase above 1.5 inches as SSE flow=20
increases off the Gulf. The combination of strong instability and=20
high PWs will favor very heavy rain rates in organized convection,
and this is supportive of the broad Slight Risk on the new=20
outlook. At the moment, model guidance is showing the most=20
consistent signal for heavy rain from Texas Hill Country in C TX=20
east- northeast into the Piney Woods region of E TX. Given the=20
overall environment, it is possible an upgrade to a Moderate Risk=20
may be needed at some point.

Lamers


Day 1 threat area: https://urldefense.com/v3/__https://www.wpc.ncep.noaa.gov/qpf/94epoints.txt= __;!!DZ3fjg!6xRxQekbUzFBT0Qg_LxjCsF7ZP3yAmkoM8lbioY-aLmehrj-mYvjVklzNW85PXg= 3fMYSpxyelbZpIe-AyurHgrfoRgw$=20
Day 2 threat area: https://urldefense.com/v3/__https://www.wpc.ncep.noaa.gov/qpf/98epoints.txt= __;!!DZ3fjg!6xRxQekbUzFBT0Qg_LxjCsF7ZP3yAmkoM8lbioY-aLmehrj-mYvjVklzNW85PXg= 3fMYSpxyelbZpIe-AyurHrhh3wFU$=20
Day 3 threat area: https://urldefense.com/v3/__https://www.wpc.ncep.noaa.gov/qpf/99epoints.txt= __;!!DZ3fjg!6xRxQekbUzFBT0Qg_LxjCsF7ZP3yAmkoM8lbioY-aLmehrj-mYvjVklzNW85PXg= 3fMYSpxyelbZpIe-AyurHnQq4WZ4$=20

=3D =3D =3D
To unsubscribe from WX-STORM and you already have a login, go to https://lists.illinois.edu and use the "Unsubscribe" link. Otherwise email Chris Novy at cnovy@cox.net and ask to be removed from WX-STORM.

--- SBBSecho 3.20-Linux
* Origin: capitolcityonline.net * Telnet/SSH:2022/HTTP (1:2320/105)

FOUS30 KWBC 010056
QPFERD

Excessive Rainfall Discussion
NWS Weather Prediction Center College Park MD
856 PM EDT Wed Apr 30 2025

Day 1
Valid 01Z Thu May 01 2025 - 12Z Thu May 01 2025

...THERE IS A MODERATE RISK OF EXCESSIVE RAINFALL FOR PORTIONS OF
NORTHEAST TEXAS AND NORTHWEST LOUISIANA...

01Z Update...

Updates to the previous ERO were based upon recent runs of the
HRRR, the 18Z HREF, and current observation trends.=20=20

The greatest heavy rain and flash flooding concerns through the
evening hours focus along the southwest flank of ongoing=20
convection and a coincident slow-moving boundary from the ArkLaTex=20 southeastward back through the Waco area. Current radar shows=20
storms training along the boundary, with rainfall rates of 1-2=20
inches/hour within some of the stronger cells. Cell-training and=20
heavy rainfall will remain a concern for at least the next few=20
hours as deep layer flow is aligned with the boundary. The Moderate
Risk was adjusted to align with the training convection, which=20
agrees well with the higher HREF neighborhood probabilities for=20
additional accumulations of 3 inches or more during the=20 evening/overnight.=20

Farther to the north across Arkansas, the threat for heavy=20
rainfall and flash flooding is diminishing where the convective=20
line has become more progressive.=20

Areas back to the north and west, where the rainfall has ended,=20
were removed from the outlook.=20

Pereira


Day 2
Valid 12Z Thu May 01 2025 - 12Z Fri May 02 2025

...THERE IS A SLIGHT RISK OF EXCESSIVE RAINFALL IN SOUTHERN
OKLAHOMA, FAR NORTH TEXAS, AND FAR WESTERN ARKANSAS...

The most significant change for this outlook period was to
introduce a Slight Risk primarily over southern Oklahoma, where
previously the probabilities were below the Marginal Risk (5
percent) threshold. This was due to an emerging consensus in model
guidance that thunderstorms will blossom on Thursday Night ahead of
a digging shortwave in an area of relatively strong upper level
divergence. Although the mid levels will be drier than in recent
days, leading to lower PWs overall, strong instability will be in
place which should support organized convection with more intense
rain rates at times. A key uncertainty at the moment is the overall
structure of convective clusters and lines, and whether they will
be more progressive or include some training. However, the
potential for heavy rain rates in an area that has received a lot
of rainfall already in recent days does raise the risk of flash
flooding. Hourly rainfall on the order of 1-2 inches will be
possible in this environment, and in areas with already wet ground
conditions this would be more than sufficient to cause flash
flooding.

Elsewhere, the broad Marginal Risk that was already in place was
maintained with few changes. A broad plume of moderate to strong
instability will favor scattered lines and clusters of
thunderstorms in advance of a surface low and trailing cold front
with fairly high instantaneous rain rates. The key uncertainty
would be the persistence of those rain rates and the degree to
which any training could occur, but the overall environment with
PWs around 1.3 to 1.4 inches raises the probability high enough to
warrant the broad Marginal Risk. The only exception to the
continuation of the risk area was over much of IL, IN, and MI,
which should largely be behind the cold front by 18Z and so most of
the QPF on model guidance would be associated with post-frontal
showers that would tend to have lower rain rates overall.

Lamers


Day 3
Valid 12Z Fri May 02 2025 - 12Z Sat May 03 2025

...THERE IS A SLIGHT RISK OF EXCESSIVE RAINFALL ACROSS FROM THE
SOUTHERN PLAINS INTO THE LOWER MISSISSIPPI VALLEY...

A flash flood event may be ongoing at the beginning of the period,
with convection developing on Thursday Night in southern Oklahoma
and continuing into Friday morning. This may continue beyond 12Z
Friday (into this Day 3 period) in SE OK and AR in the region of
strong upper-level divergence. The existing Slight Risk over TX was
expanded northward to account for this scenario. Whether that round
of convection wanes due to more extensive cloud cover and limited
daytime heating, or progresses southeast and becomes reinvigorated
during the afternoon, the threat of heavy rainfall and flash
flooding should expand southeast on Friday into the Lower
Mississippi Valley (S AR, N LA, W MS) and much of C and E TX. This
would be via progression of the early round of storms, or
redevelopment in the afternoon and evening hours.

Strong instability will remain over much of the warm sector with
CAPE values potentially in excess of 3000 j/kg in some areas, and
PW values are expected to increase above 1.5 inches as SSE flow
increases off the Gulf. The combination of strong instability and
high PWs will favor very heavy rain rates in organized convection,
and this is supportive of the broad Slight Risk on the new
outlook. At the moment, model guidance is showing the most
consistent signal for heavy rain from Texas Hill Country in C TX
east- northeast into the Piney Woods region of E TX. Given the
overall environment, it is possible an upgrade to a Moderate Risk
may be needed at some point.

Lamers


Day 1 threat area: https://urldefense.com/v3/__https://www.wpc.ncep.noaa.gov/qpf/94epoints.txt= __;!!DZ3fjg!7GGFWblYIR9ZVeED1qsQ6kYKtQebZ_rOKbf9URzJpWCAkrV2GcUPVpJxjYZfBf7= g3PhStlk-DOCQlMHU_cs9IV9iHwg$=20
Day 2 threat area: https://urldefense.com/v3/__https://www.wpc.ncep.noaa.gov/qpf/98epoints.txt= __;!!DZ3fjg!7GGFWblYIR9ZVeED1qsQ6kYKtQebZ_rOKbf9URzJpWCAkrV2GcUPVpJxjYZfBf7= g3PhStlk-DOCQlMHU_cs91RK5-hQ$=20
Day 3 threat area: https://urldefense.com/v3/__https://www.wpc.ncep.noaa.gov/qpf/99epoints.txt= __;!!DZ3fjg!7GGFWblYIR9ZVeED1qsQ6kYKtQebZ_rOKbf9URzJpWCAkrV2GcUPVpJxjYZfBf7= g3PhStlk-DOCQlMHU_cs9s9kfUco$=20

=3D =3D =3D
To unsubscribe from WX-STORM and you already have a login, go to https://lists.illinois.edu and use the "Unsubscribe" link. Otherwise email Chris Novy at cnovy@cox.net and ask to be removed from WX-STORM.

--- SBBSecho 3.20-Linux
* Origin: capitolcityonline.net * Telnet/SSH:2022/HTTP (1:2320/105)

FOUS30 KWBC 010756
QPFERD

Excessive Rainfall Discussion
NWS Weather Prediction Center College Park MD
356 AM EDT Thu May 1 2025

Day 1
Valid 12Z Thu May 01 2025 - 12Z Fri May 02 2025

...THERE IS A SLIGHT RISK OF EXCESSIVE RAINFALL IN SOUTHERN
OKLAHOMA, FAR NORTH TEXAS, FAR WESTERN ARKANSAS, WESTERN
PENNSYLVANIA AND THE CENTRAL APPALACHIANS...

...Southern Plains...

Shortwave ejection out of the Southern Rockies will interact with a
cold front pressing south through the Central and Southern Plains
by the late-afternoon and evening hours Thursday through Friday
morning. A relevant theta_E differential will be aligned within=20
the confines of the boundary providing a suitable thermodynamic=20
alignment such that area convection anchors and pushes along the=20
west to east oriented instability gradient across Southern OK.
Majority of CAMs are in consensus of a heavy rainfall footprint
along and south of I-40, generally configured to the timing of the
cold front, shortwave interaction, and LLJ convergence signal. This
is primarily right around 00z when the convective threat enhances
with the integration of the nocturnal LLJ, a timing historically
prevalent for this time of year and this setup is no exception.

00z HREF neighborhood probs for >1" are relatively high (50-80%)=20
within the corridor extending from Southwest OK across the Red=20
River Basin towards the AR border. >2" is highest just north of the
river from I-35 on east, a testament to the timing of the
shortwave arrival and upscale growth of the convective threat as it
maneuvers to the east-southeast. Rainfall rates between 1-2"/hr are
most likely when assessing the hourly rate probs from the both the
NBM and HREF output, a rate assessment that is more than suitable
considering the blanket low FFG intervals due to the antecedent
moist soils from the past 36-48 hrs of rainfall. The areal QPF=20
footprint of >1" aligned within those lower FFG's pretty much
perfectly, a scenario that lends to a greater credence of a touch
higher risk category that what is normal the case for this setup.
The previous SLGT risk was relatively maintained with minor
adjustments on the edges pertaining to recent hi-res QPF and in
conjunction with the ML First Guess Fields.=20

...Interior Mid Atlantic...

Shortwave trough currently positioned over the Southern Plains will
lift northeast through the Mississippi Valley with sights on the
Great Lakes region by the second half of the D1. Downstream, an
improved diffluent signature will align over the Ohio Valley and
points northeast allowing for regional ascent to boost convective
initiation in-of places within that diffluent core. The most
notable area for convective development lies within an established
theta_E tongue riding northward through the Appalachians Front=20
with poleward expansion into the southeastern Great Lakes. This=20
allowed for moisture rich air exuding PWAT anomalies between +2 and
+3 within the corridor extending through much of WV up through=20
Eastern OH and Western PA to the Lake Erie border. SBCAPE between=20
1500-2500 J/kg will be a common occurrence during peak diurnal=20 destabilization creating a corridor of enhanced thermodynamic=20
prospects to coincide with the arrival of the better mid-level=20
forcing downstream of the approaching trough. Regional shear will=20
be improving as well, especially within the confines of a shallow=20
warm front that will be lifting northward through the course of the
afternoon across the interior Mid Atlantic. Cell initiation will=20
begin between 18-00z today with greater multi-cell cluster coverage
likely to occur towards the back end of the above time frame due=20
to anchoring along the warm front as it approaches. Areas across=20
Western PA have been hit relatively hard recently with convective=20
rainfall adding to the areal decoupling of the FFG indices meaning=20
the prospects for flash flooding have increased with the arrival of
this next disturbance.

00z HREF neighborhood probs for >2" are between 30-50% across a
large section of Western PA extending south into the northern High
Country of WV, rooted in the Appalachians Front, an area notorious
for flashy rivers and smaller towns located within the valleys.
There was enough consensus to warrant an upgrade considering the
antecedent conditions, atmospheric environmental favorability, as
well as the increased probs denoting a locally heavy rain prospect
over the region. A SLGT risk has been added to much of Western PA
down into portions of the Central Appalachians.=20

Kleebauer


Day 2
Valid 12Z Fri May 02 2025 - 12Z Sat May 03 2025

...THERE IS A SLIGHT RISK OF EXCESSIVE RAINFALL ACROSS FROM THE
SOUTHERN PLAINS INTO THE LOWER MISSISSIPPI VALLEY...

Steady progression of a cold front through the Southern Plains will
lead to textbook convergent pattern with an addition of a strong=20
upper diffluence signature within the bounds of the southern jet
proxy. High areal theta_E averages will denote the significant=20
instability pattern positioned ahead of the approaching cold front=20
leading to ample thermodynamic assistance for strong convective=20
cores and expected heavy rainfall. Recent CAMs have finally come=20
into view for the primary window of cell initiation with a
widespread convective pattern likely to extend from the Stockton
Plateau to points east within the I-10 corridor up through all of
Hill Country, especially over the I-35 section of south-central TX.
HREF blended mean QPF is over 2" now within a large area=20
encompassing the terrain focused across the Central portion of the
state. This had led to elevated neighborhood probs of >2" for the=20
12-00z time frame in the forecast running >70% over pretty much all
of the above region extending into portions of East TX. The East TX
corridor has become a newer development in terms of anticipated QPF
magnitude as the the CAMs and in some instances the global
deterministic are now catching on to the deep moisture advection
regime poking north out of the Western Gulf ahead of the front
arrival. Forecast soundings across the area between Houston up to
the latitude of Austin are now indicating MUCAPE or the order of
3500-5000 J/kg prior to any front arrival leading to significant
heavy cores to transpire due to cap breach from diurnal
destabilization initially, followed by more organized multi-cell
clusters as we move into the evening as the LLJ re-intensifies and
the cold front motions into the region.=20

Soundings also note a period of mean flow and upshear components
that would lead to potential backbuilding within the confines of
the front. Very strong ascent between 850-300mb is also noted
within multiple CAMs outputs, a testament to the favorability for
the setup to become more organized and providing a vast areal
expanse of heavy convection once the setup matures. PWATs between
1.6-1.9" with locally >2" are being forecast along and ahead of the
front as it moves into Central TX, a forecast that traditionally is
favored for greater flash flood prospects, especially over the
favored I-35 corridor between Austin to San Antonio where high
runoff capabilities are found due to soil type and limestone
foundations. Local totals between 3-6" are likely over the entire
stretch of Hill Country through East TX with the eastern most
extent even shifting into Western LA as the convective pattern
evolves and grows upscale entering into the adjacent Lower
Mississippi Valley. Houston metro is now in play for convective
impacts, especially as thunderstorms to the north provide outflow
generation that could send cold pools south towards the Gulf coast
with additional convective development along the edge of any
approaching cold pool.=20

The previous SLGT risk was relatively unchanged across Central TX.
Some expansion to the west was made into the Stockton Plateau where
initial cell formations will likely occur as the front arrives and
interacts with a formidable instability axis aligned over the
plateau itself. The SLGT was expanded southeast to cover the
Houston metro and points north where there is growing consensus on
convective impacts over and near the urban center. This is a high-
end SLGT over much of Central TX, especially Hill Country to the
I-35 corridor and points east. A risk upgrade is not out of the
question in subsequent updates given the environmental
favorability and flashy history of places expected to see the
greatest thunderstorm coverage/rates.=20=20

Kleebauer


Day 3
Valid 12Z Sat May 03 2025 - 12Z Sun May 04 2025

...THERE IS A MARGINAL RISK OF EXCESSIVE RAINFALL ACROSS MUCH OF
THE APPALACHIAN FRONT AS WELL AS PORTIONS OF THE GREAT BASIN...

...Appalachians...

An anomalous upper low center evolving over the Ohio Valley will
generate a strong diffluent signature downstream across the
Appalachians and points east with a significant moisture fetch
poleward from the Gulf, and eventual Atlantic Basin by the end of=20
the period. Organized convective activity will brew within the RER
of a strengthening upper jet core located over Ontario/Quebec as
the upper pattern becomes closed off to the west after 00z/Sun.
NAEFS PWAT anomalies between +1 and +2 deviations will offer a
suitable moisture rich environment conducive for stronger heavy
convective cores capable of locally enhanced rainfall prospects
within the confines of the great diffluent axis. As of this time,
this places the Appalachians Front from Northern GA up through PA=20
as the primary region of interest, however some elevated=20
instability notions are present within some of the recent=20
deterministic output. As of this time, a general 1-2" is forecast=20
within the above corridor with some heavier cells even possible as=20
far south as the Central Gulf Coast, but those are more aligned=20
within the decaying surface front that is progged to breakdown=20
before exiting the coastal plain. The area of focus will reside=20
within that broad ascent pattern enhanced by the evolving amplified
pattern to the east of the Mississippi with the complex terrain=20
providing a secondary element that would favor isolated flash flood
prospects. As a result, a broad MRGL risk extends from the=20
Southern Appalachians up through Northeast PA where the current=20
ensemble mean QPF is highest while also residing within the lower=20
FFG indices available in the Eastern CONUS.

...Great Basin...

Omega block pattern initiating over the CONUS will lead to yet
another amplified upper low generation across the Western CONUS
through D3. The threat for elevated convection in-of interior NV up
into Southeast OR have been forecast for several days with the
deterministic guidance basically "locked in" to the expected
evolution. Despite rainfall rates rather low grade compared to what
you normally find for flash flooding, this area has a notorious low
FFG bias that tends to accentuate the flash flood prospects in this
area of the CONUS. Recent ensemble means have been hovering between
0.75-1.25" of total QPF within the corridor extending from Reno to
points northeast with local maxima hovering up near 2" due to the
added effect of greater upper forcing thanks to the maturing closed
ULL reflection. This setup has been steady within the First Guess
Fields for the threat and really hasn't wavered much in the MRGL
risk output from the ML. Considering the factors above and a
pattern more favorable for these convective schemes across the
Great Basin, the previous MRGL risk inherited was maintained with a
small expansion northward into Southeast OR to highlight QPF trends
favoring better totals within those zones.=20

Kleebauer


Day 1 threat area: https://urldefense.com/v3/__https://www.wpc.ncep.noaa.gov/qpf/94epoints.txt= __;!!DZ3fjg!5tLfNxQDfhASy9a9otxw4b2kJ6vctypwG6Txq5vOh2EQ-J_DPdmjxslVr3SmtzD= dsR7ZHhAvfVbdF-8krIv8Hr8XXYQ$=20
Day 2 threat area: https://urldefense.com/v3/__https://www.wpc.ncep.noaa.gov/qpf/98epoints.txt= __;!!DZ3fjg!5tLfNxQDfhASy9a9otxw4b2kJ6vctypwG6Txq5vOh2EQ-J_DPdmjxslVr3SmtzD= dsR7ZHhAvfVbdF-8krIv8EESmbY8$=20
Day 3 threat area: https://urldefense.com/v3/__https://www.wpc.ncep.noaa.gov/qpf/99epoints.txt= __;!!DZ3fjg!5tLfNxQDfhASy9a9otxw4b2kJ6vctypwG6Txq5vOh2EQ-J_DPdmjxslVr3SmtzD= dsR7ZHhAvfVbdF-8krIv8JFHS_qk$=20

=3D =3D =3D
To unsubscribe from WX-STORM and you already have a login, go to https://lists.illinois.edu and use the "Unsubscribe" link. Otherwise email Chris Novy at cnovy@cox.net and ask to be removed from WX-STORM.

--- SBBSecho 3.20-Linux
* Origin: capitolcityonline.net * Telnet/SSH:2022/HTTP (1:2320/105)

FOUS30 KWBC 011551
QPFERD

Excessive Rainfall Discussion
NWS Weather Prediction Center College Park MD
1151 AM EDT Thu May 1 2025

Day 1
Valid 16Z Thu May 01 2025 - 12Z Fri May 02 2025

...THERE IS A SLIGHT RISK OF EXCESSIVE RAINFALL FOR SOUTHERN=20
OKLAHOMA AND FAR WESTERN ARKANSAS AS WELL AS FOR PORTIONS OF THE CENTRAL APPALACHIANS...

...16Z Update...

Only very minor tweaks were needed to the Slight Risk areas across
the Southern Plains and central Appalachians. For the southern
Plains, the 12Z HiRes guidance shifted very slightly (10-20 miles)
north with tonight's expected MCS development across Oklahoma.
Given the high sensitivity of that entire area between Dallas and
Oklahoma City for heavy rainfall, the Slight Risk was maintained.
The 12Z HRRR followed previous runs suggesting there may be
training showers that get hung up on the southern end of the MCS
just north of the Red River, but by then the instability should be
largely used up and therefore rates should come down a bit. Given
that, the Slight was maintained with no upgrades...though it
wouldn't take much of an uptick in future guidance to possibly need
a targeted Moderate, depending on if the guidance can come into
better agreement on where the axis of heaviest rain will set up.

Over to the Central Appalachians, the guidance unfortunately
remains in poorer agreement than in the southern Plains. Expect
more widely scattered convection to impact the area starting this
afternoon, developing into one or more lines of storms by the
evening. Each line will be very progressive/fast-moving, so
individual storms will not have much of a flooding impact. However,
with multiple rounds of showers and storms expected in an area
recently hard hit with heavy rain, the multiple rounds of storms
may collectively add up to widely scattered instances of flash
flooding into this evening. The inherited Slight was trimmed in
MD/WV out of areas east of the Allegheny Front, which are
significantly drier and with higher FFGs than areas along and west.

Wegman

...Previous Discussion...

...Southern Plains...

Shortwave ejection out of the Southern Rockies will interact with a
cold front pressing south through the Central and Southern Plains
by the late-afternoon and evening hours Thursday through Friday
morning. A relevant theta_E differential will be aligned within
the confines of the boundary providing a suitable thermodynamic
alignment such that area convection anchors and pushes along the
west to east oriented instability gradient across Southern OK.
Majority of CAMs are in consensus of a heavy rainfall footprint
along and south of I-40, generally configured to the timing of the
cold front, shortwave interaction, and LLJ convergence signal. This
is primarily right around 00z when the convective threat enhances
with the integration of the nocturnal LLJ, a timing historically
prevalent for this time of year and this setup is no exception.

00z HREF neighborhood probs for >1" are relatively high (50-80%)
within the corridor extending from Southwest OK across the Red
River Basin towards the AR border. >2" is highest just north of the
river from I-35 on east, a testament to the timing of the
shortwave arrival and upscale growth of the convective threat as it
maneuvers to the east-southeast. Rainfall rates between 1-2"/hr are
most likely when assessing the hourly rate probs from the both the
NBM and HREF output, a rate assessment that is more than suitable
considering the blanket low FFG intervals due to the antecedent
moist soils from the past 36-48 hrs of rainfall. The areal QPF
footprint of >1" aligned within those lower FFG's pretty much
perfectly, a scenario that lends to a greater credence of a touch
higher risk category that what is normal the case for this setup.
The previous SLGT risk was relatively maintained with minor
adjustments on the edges pertaining to recent hi-res QPF and in
conjunction with the ML First Guess Fields.

...Interior Mid Atlantic...

Shortwave trough currently positioned over the Southern Plains will
lift northeast through the Mississippi Valley with sights on the
Great Lakes region by the second half of the D1. Downstream, an
improved diffluent signature will align over the Ohio Valley and
points northeast allowing for regional ascent to boost convective
initiation in-of places within that diffluent core. The most
notable area for convective development lies within an established
theta_E tongue riding northward through the Appalachians Front
with poleward expansion into the southeastern Great Lakes. This
allowed for moisture rich air exuding PWAT anomalies between +2 and
+3 within the corridor extending through much of WV up through
Eastern OH and Western PA to the Lake Erie border. SBCAPE between
1500-2500 J/kg will be a common occurrence during peak diurnal
destabilization creating a corridor of enhanced thermodynamic
prospects to coincide with the arrival of the better mid-level
forcing downstream of the approaching trough. Regional shear will
be improving as well, especially within the confines of a shallow
warm front that will be lifting northward through the course of the
afternoon across the interior Mid Atlantic. Cell initiation will
begin between 18-00z today with greater multi-cell cluster coverage
likely to occur towards the back end of the above time frame due
to anchoring along the warm front as it approaches. Areas across
Western PA have been hit relatively hard recently with convective
rainfall adding to the areal decoupling of the FFG indices meaning
the prospects for flash flooding have increased with the arrival of
this next disturbance.

00z HREF neighborhood probs for >2" are between 30-50% across a
large section of Western PA extending south into the northern High
Country of WV, rooted in the Appalachians Front, an area notorious
for flashy rivers and smaller towns located within the valleys.
There was enough consensus to warrant an upgrade considering the
antecedent conditions, atmospheric environmental favorability, as
well as the increased probs denoting a locally heavy rain prospect
over the region. A SLGT risk has been added to much of Western PA
down into portions of the Central Appalachians.

Kleebauer


Day 2
Valid 12Z Fri May 02 2025 - 12Z Sat May 03 2025

...THERE IS A SLIGHT RISK OF EXCESSIVE RAINFALL ACROSS FROM THE
SOUTHERN PLAINS INTO THE LOWER MISSISSIPPI VALLEY...

Steady progression of a cold front through the Southern Plains will
lead to textbook convergent pattern with an addition of a strong
upper diffluence signature within the bounds of the southern jet
proxy. High areal theta_E averages will denote the significant
instability pattern positioned ahead of the approaching cold front
leading to ample thermodynamic assistance for strong convective
cores and expected heavy rainfall. Recent CAMs have finally come
into view for the primary window of cell initiation with a
widespread convective pattern likely to extend from the Stockton
Plateau to points east within the I-10 corridor up through all of
Hill Country, especially over the I-35 section of south-central TX.
HREF blended mean QPF is over 2" now within a large area
encompassing the terrain focused across the Central portion of the
state. This had led to elevated neighborhood probs of >2" for the
12-00z time frame in the forecast running >70% over pretty much all
of the above region extending into portions of East TX. The East TX
corridor has become a newer development in terms of anticipated QPF
magnitude as the the CAMs and in some instances the global
deterministic are now catching on to the deep moisture advection
regime poking north out of the Western Gulf ahead of the front
arrival. Forecast soundings across the area between Houston up to
the latitude of Austin are now indicating MUCAPE or the order of
3500-5000 J/kg prior to any front arrival leading to significant
heavy cores to transpire due to cap breach from diurnal
destabilization initially, followed by more organized multi-cell
clusters as we move into the evening as the LLJ re-intensifies and
the cold front motions into the region.

Soundings also note a period of mean flow and upshear components
that would lead to potential backbuilding within the confines of
the front. Very strong ascent between 850-300mb is also noted
within multiple CAMs outputs, a testament to the favorability for
the setup to become more organized and providing a vast areal
expanse of heavy convection once the setup matures. PWATs between
1.6-1.9" with locally >2" are being forecast along and ahead of the
front as it moves into Central TX, a forecast that traditionally is
favored for greater flash flood prospects, especially over the
favored I-35 corridor between Austin to San Antonio where high
runoff capabilities are found due to soil type and limestone
foundations. Local totals between 3-6" are likely over the entire
stretch of Hill Country through East TX with the eastern most
extent even shifting into Western LA as the convective pattern
evolves and grows upscale entering into the adjacent Lower
Mississippi Valley. Houston metro is now in play for convective
impacts, especially as thunderstorms to the north provide outflow
generation that could send cold pools south towards the Gulf coast
with additional convective development along the edge of any
approaching cold pool.

The previous SLGT risk was relatively unchanged across Central TX.
Some expansion to the west was made into the Stockton Plateau where
initial cell formations will likely occur as the front arrives and
interacts with a formidable instability axis aligned over the
plateau itself. The SLGT was expanded southeast to cover the
Houston metro and points north where there is growing consensus on
convective impacts over and near the urban center. This is a high-
end SLGT over much of Central TX, especially Hill Country to the
I-35 corridor and points east. A risk upgrade is not out of the
question in subsequent updates given the environmental
favorability and flashy history of places expected to see the
greatest thunderstorm coverage/rates.

Kleebauer


Day 3
Valid 12Z Sat May 03 2025 - 12Z Sun May 04 2025

...THERE IS A MARGINAL RISK OF EXCESSIVE RAINFALL ACROSS MUCH OF
THE APPALACHIAN FRONT AS WELL AS PORTIONS OF THE GREAT BASIN...

...Appalachians...

An anomalous upper low center evolving over the Ohio Valley will
generate a strong diffluent signature downstream across the
Appalachians and points east with a significant moisture fetch
poleward from the Gulf, and eventual Atlantic Basin by the end of
the period. Organized convective activity will brew within the RER
of a strengthening upper jet core located over Ontario/Quebec as
the upper pattern becomes closed off to the west after 00z/Sun.
NAEFS PWAT anomalies between +1 and +2 deviations will offer a
suitable moisture rich environment conducive for stronger heavy
convective cores capable of locally enhanced rainfall prospects
within the confines of the great diffluent axis. As of this time,
this places the Appalachians Front from Northern GA up through PA
as the primary region of interest, however some elevated
instability notions are present within some of the recent
deterministic output. As of this time, a general 1-2" is forecast
within the above corridor with some heavier cells even possible as
far south as the Central Gulf Coast, but those are more aligned
within the decaying surface front that is progged to breakdown
before exiting the coastal plain. The area of focus will reside
within that broad ascent pattern enhanced by the evolving amplified
pattern to the east of the Mississippi with the complex terrain
providing a secondary element that would favor isolated flash flood
prospects. As a result, a broad MRGL risk extends from the
Southern Appalachians up through Northeast PA where the current
ensemble mean QPF is highest while also residing within the lower
FFG indices available in the Eastern CONUS.

...Great Basin...

Omega block pattern initiating over the CONUS will lead to yet
another amplified upper low generation across the Western CONUS
through D3. The threat for elevated convection in-of interior NV up
into Southeast OR have been forecast for several days with the
deterministic guidance basically "locked in" to the expected
evolution. Despite rainfall rates rather low grade compared to what
you normally find for flash flooding, this area has a notorious low
FFG bias that tends to accentuate the flash flood prospects in this
area of the CONUS. Recent ensemble means have been hovering between
0.75-1.25" of total QPF within the corridor extending from Reno to
points northeast with local maxima hovering up near 2" due to the
added effect of greater upper forcing thanks to the maturing closed
ULL reflection. This setup has been steady within the First Guess
Fields for the threat and really hasn't wavered much in the MRGL
risk output from the ML. Considering the factors above and a
pattern more favorable for these convective schemes across the
Great Basin, the previous MRGL risk inherited was maintained with a
small expansion northward into Southeast OR to highlight QPF trends
favoring better totals within those zones.

Kleebauer


Day 1 threat area: https://urldefense.com/v3/__https://www.wpc.ncep.noaa.gov/qpf/94epoints.txt= __;!!DZ3fjg!43nye14i9bdePWxTDqZD-ySGdhEqdHxYGNyW8Y6xlsI9crcMbF3lJxAL1XPyNHk= PUCVLVH8lJb_JohZUcwuTfRKLPj0$=20
Day 2 threat area: https://urldefense.com/v3/__https://www.wpc.ncep.noaa.gov/qpf/98epoints.txt= __;!!DZ3fjg!43nye14i9bdePWxTDqZD-ySGdhEqdHxYGNyW8Y6xlsI9crcMbF3lJxAL1XPyNHk= PUCVLVH8lJb_JohZUcwuT9EqYsD4$=20
Day 3 threat area: https://urldefense.com/v3/__https://www.wpc.ncep.noaa.gov/qpf/99epoints.txt= __;!!DZ3fjg!43nye14i9bdePWxTDqZD-ySGdhEqdHxYGNyW8Y6xlsI9crcMbF3lJxAL1XPyNHk= PUCVLVH8lJb_JohZUcwuTvk0gzAQ$=20

=3D =3D =3D
To unsubscribe from WX-STORM and you already have a login, go to https://lists.illinois.edu and use the "Unsubscribe" link. Otherwise email Chris Novy at cnovy@cox.net and ask to be removed from WX-STORM.

--- SBBSecho 3.20-Linux
* Origin: capitolcityonline.net * Telnet/SSH:2022/HTTP (1:2320/105)

FOUS30 KWBC 011945
QPFERD

Excessive Rainfall Discussion
NWS Weather Prediction Center College Park MD
345 PM EDT Thu May 1 2025

Day 1
Valid 16Z Thu May 01 2025 - 12Z Fri May 02 2025

...THERE IS A SLIGHT RISK OF EXCESSIVE RAINFALL FOR SOUTHERN
OKLAHOMA AND FAR WESTERN ARKANSAS AS WELL AS FOR PORTIONS OF THE CENTRAL APPALACHIANS...

...16Z Update...

Only very minor tweaks were needed to the Slight Risk areas across
the Southern Plains and central Appalachians. For the southern
Plains, the 12Z HiRes guidance shifted very slightly (10-20 miles)
north with tonight's expected MCS development across Oklahoma.
Given the high sensitivity of that entire area between Dallas and
Oklahoma City for heavy rainfall, the Slight Risk was maintained.
The 12Z HRRR followed previous runs suggesting there may be
training showers that get hung up on the southern end of the MCS
just north of the Red River, but by then the instability should be
largely used up and therefore rates should come down a bit. Given
that, the Slight was maintained with no upgrades...though it
wouldn't take much of an uptick in future guidance to possibly need
a targeted Moderate, depending on if the guidance can come into
better agreement on where the axis of heaviest rain will set up.

Over to the Central Appalachians, the guidance unfortunately
remains in poorer agreement than in the southern Plains. Expect
more widely scattered convection to impact the area starting this
afternoon, developing into one or more lines of storms by the
evening. Each line will be very progressive/fast-moving, so
individual storms will not have much of a flooding impact. However,
with multiple rounds of showers and storms expected in an area
recently hard hit with heavy rain, the multiple rounds of storms
may collectively add up to widely scattered instances of flash
flooding into this evening. The inherited Slight was trimmed in
MD/WV out of areas east of the Allegheny Front, which are
significantly drier and with higher FFGs than areas along and west.

Wegman

...Previous Discussion...

...Southern Plains...

Shortwave ejection out of the Southern Rockies will interact with a
cold front pressing south through the Central and Southern Plains
by the late-afternoon and evening hours Thursday through Friday
morning. A relevant theta_E differential will be aligned within
the confines of the boundary providing a suitable thermodynamic
alignment such that area convection anchors and pushes along the
west to east oriented instability gradient across Southern OK.
Majority of CAMs are in consensus of a heavy rainfall footprint
along and south of I-40, generally configured to the timing of the
cold front, shortwave interaction, and LLJ convergence signal. This
is primarily right around 00z when the convective threat enhances
with the integration of the nocturnal LLJ, a timing historically
prevalent for this time of year and this setup is no exception.

00z HREF neighborhood probs for >1" are relatively high (50-80%)
within the corridor extending from Southwest OK across the Red
River Basin towards the AR border. >2" is highest just north of the
river from I-35 on east, a testament to the timing of the
shortwave arrival and upscale growth of the convective threat as it
maneuvers to the east-southeast. Rainfall rates between 1-2"/hr are
most likely when assessing the hourly rate probs from the both the
NBM and HREF output, a rate assessment that is more than suitable
considering the blanket low FFG intervals due to the antecedent
moist soils from the past 36-48 hrs of rainfall. The areal QPF
footprint of >1" aligned within those lower FFG's pretty much
perfectly, a scenario that lends to a greater credence of a touch
higher risk category that what is normal the case for this setup.
The previous SLGT risk was relatively maintained with minor
adjustments on the edges pertaining to recent hi-res QPF and in
conjunction with the ML First Guess Fields.

...Interior Mid Atlantic...

Shortwave trough currently positioned over the Southern Plains will
lift northeast through the Mississippi Valley with sights on the
Great Lakes region by the second half of the D1. Downstream, an
improved diffluent signature will align over the Ohio Valley and
points northeast allowing for regional ascent to boost convective
initiation in-of places within that diffluent core. The most
notable area for convective development lies within an established
theta_E tongue riding northward through the Appalachians Front
with poleward expansion into the southeastern Great Lakes. This
allowed for moisture rich air exuding PWAT anomalies between +2 and
+3 within the corridor extending through much of WV up through
Eastern OH and Western PA to the Lake Erie border. SBCAPE between
1500-2500 J/kg will be a common occurrence during peak diurnal
destabilization creating a corridor of enhanced thermodynamic
prospects to coincide with the arrival of the better mid-level
forcing downstream of the approaching trough. Regional shear will
be improving as well, especially within the confines of a shallow
warm front that will be lifting northward through the course of the
afternoon across the interior Mid Atlantic. Cell initiation will
begin between 18-00z today with greater multi-cell cluster coverage
likely to occur towards the back end of the above time frame due
to anchoring along the warm front as it approaches. Areas across
Western PA have been hit relatively hard recently with convective
rainfall adding to the areal decoupling of the FFG indices meaning
the prospects for flash flooding have increased with the arrival of
this next disturbance.

00z HREF neighborhood probs for >2" are between 30-50% across a
large section of Western PA extending south into the northern High
Country of WV, rooted in the Appalachians Front, an area notorious
for flashy rivers and smaller towns located within the valleys.
There was enough consensus to warrant an upgrade considering the
antecedent conditions, atmospheric environmental favorability, as
well as the increased probs denoting a locally heavy rain prospect
over the region. A SLGT risk has been added to much of Western PA
down into portions of the Central Appalachians.

Kleebauer


Day 2
Valid 12Z Fri May 02 2025 - 12Z Sat May 03 2025

...THERE IS A SLIGHT RISK OF EXCESSIVE RAINFALL ACROSS FROM THE
SOUTHERN PLAINS INTO THE LOWER MISSISSIPPI VALLEY...

...20Z Update...

A small southward nudge to the inherited Slight was added with this
update, with the Slight now including all of the upper Texas Gulf
Coast. A higher end Slight (not depicted) is in effect for the San
Antonio metro north and east, including the Houston Metro and into
northern and western Louisiana.=20

Overall very few changes were needed to the inherited risk areas.
The Slight Risk remains for much of Texas, from portions of the Rio
Grande Valley north and east to the Memphis metro. The heaviest
rains will be associated with a southward moving line of storms
with a cold front that will develop across central Texas Friday=20
afternoon and progress south and east to the Gulf Coast into Friday
night. Plentiful Gulf moisture ahead of the line with PWATs to 1.75
inches around the Houston metro and MUCAPE values well above 2,000
J/kg will favor very heavy rainfall rates with the strongest cores
of storms capable of over 2 inches per hour rain rates.
Fortunately, most of these areas of Texas have been drier than
areas to the north towards Oklahoma, so the lack of overlap with
previous rounds of heavy rain precluded the need for any Moderate
Risk upgrades this afternoon. There is some agreement in the
guidance that the heavy rain axis associated with the potential for
some limited training will remain just north of Houston in the Big
Thicket region. So long as this remains north of the most populated
areas around Houston then the Slight Risk should be sufficient, but
too much of a southward shift in that heavy rain axis would move
the threat into more urbanized areas, in which case a Moderate Risk
may be needed. 12Z HREF guidance shows an over 70% chance of 3
inches or more of rain in the neighborhood probabilities from just
west of the Louisiana border to Austin, remaining just north of
I-10.=20

The cold front driving these storms will advect much drier air into
much of Oklahoma and north Texas, which will greatly diminish any
storm threat in that area. For southeast Oklahoma, the threat is
largely Friday morning with lingering convection from the MCS that
will be progressing southeastward into northeast Texas and southern Arkansas/northern Louisiana.

Storms will be less organized and much faster moving progressing
northeast into the central Appalachians/western Pennsylvania. Thus,
despite low FFGs from recent heavy rains, the Marginal should
suffice for that area. Of course, should the storms slow down or
develop into multiple rounds, then a Slight will be needed.
Nonetheless, potential for heavy rains over saturated soils did
necessitate a small expansion of the Marginal to the southern Tier
of western New York.

Wegman

...Previous Discussion...

Steady progression of a cold front through the Southern Plains will
lead to textbook convergent pattern with an addition of a strong
upper diffluence signature within the bounds of the southern jet
proxy. High areal theta_E averages will denote the significant
instability pattern positioned ahead of the approaching cold front
leading to ample thermodynamic assistance for strong convective
cores and expected heavy rainfall. Recent CAMs have finally come
into view for the primary window of cell initiation with a
widespread convective pattern likely to extend from the Stockton
Plateau to points east within the I-10 corridor up through all of
Hill Country, especially over the I-35 section of south-central TX.
HREF blended mean QPF is over 2" now within a large area
encompassing the terrain focused across the Central portion of the
state. This had led to elevated neighborhood probs of >2" for the
12-00z time frame in the forecast running >70% over pretty much all
of the above region extending into portions of East TX. The East TX
corridor has become a newer development in terms of anticipated QPF
magnitude as the the CAMs and in some instances the global
deterministic are now catching on to the deep moisture advection
regime poking north out of the Western Gulf ahead of the front
arrival. Forecast soundings across the area between Houston up to
the latitude of Austin are now indicating MUCAPE or the order of
3500-5000 J/kg prior to any front arrival leading to significant
heavy cores to transpire due to cap breach from diurnal
destabilization initially, followed by more organized multi-cell
clusters as we move into the evening as the LLJ re-intensifies and
the cold front motions into the region.

Soundings also note a period of mean flow and upshear components
that would lead to potential backbuilding within the confines of
the front. Very strong ascent between 850-300mb is also noted
within multiple CAMs outputs, a testament to the favorability for
the setup to become more organized and providing a vast areal
expanse of heavy convection once the setup matures. PWATs between
1.6-1.9" with locally >2" are being forecast along and ahead of the
front as it moves into Central TX, a forecast that traditionally is
favored for greater flash flood prospects, especially over the
favored I-35 corridor between Austin to San Antonio where high
runoff capabilities are found due to soil type and limestone
foundations. Local totals between 3-6" are likely over the entire
stretch of Hill Country through East TX with the eastern most
extent even shifting into Western LA as the convective pattern
evolves and grows upscale entering into the adjacent Lower
Mississippi Valley. Houston metro is now in play for convective
impacts, especially as thunderstorms to the north provide outflow
generation that could send cold pools south towards the Gulf coast
with additional convective development along the edge of any
approaching cold pool.

The previous SLGT risk was relatively unchanged across Central TX.
Some expansion to the west was made into the Stockton Plateau where
initial cell formations will likely occur as the front arrives and
interacts with a formidable instability axis aligned over the
plateau itself. The SLGT was expanded southeast to cover the
Houston metro and points north where there is growing consensus on
convective impacts over and near the urban center. This is a high-
end SLGT over much of Central TX, especially Hill Country to the
I-35 corridor and points east. A risk upgrade is not out of the
question in subsequent updates given the environmental
favorability and flashy history of places expected to see the
greatest thunderstorm coverage/rates.

Kleebauer


Day 3
Valid 12Z Sat May 03 2025 - 12Z Sun May 04 2025

...THERE IS A MARGINAL RISK OF EXCESSIVE RAINFALL FROM THE CENTRAL
GULF COAST TO THE CENTRAL APPALACHIANS AS WELL AS PORTIONS OF THE=20
GREAT BASIN...

...20Z Update...

The inherited Marginal Risk was expanded south to the central Gulf
Coast with this update, with no changes towards the Great Basin.

Ongoing convection at the start of the period will impact the
central Gulf Coast on Saturday morning. While this area can take a
lot of rain before there are significant flooding issues, the
urbanization along the coast should support isolated instances of
flash flooding from New Orleans through Pensacola. Additional
afternoon convection will develop all throughout the Marginal Risk
area Saturday afternoon from the Gulf Coast through New York.
Topographic concerns and urban areas will be at higher risk for
potential flash flooding, but the otherwise progressive nature of
the storms should preclude more than isolated flash flooding in the
Marginal Risk area. PWATs over 1.5 inches from the Gulf Coast into
central Alabama and western Georgia would favor the most storms
capable of heavy rainfall. Depending on how much rainfall falls
along the Gulf Coast, especially through Mobile Friday night, the
additional rainfall Saturday could necessitate a Slight Risk
issuance with future updates from southern Alabama roughly to the
Atlanta area. Meanwhile further north once again the storms look to
be progressive enough that only isolated instances of flash
flooding are expected, including into western Pennsylvania.

Wegman

...Previous Discussion...

...Appalachians...

An anomalous upper low center evolving over the Ohio Valley will
generate a strong diffluent signature downstream across the
Appalachians and points east with a significant moisture fetch
poleward from the Gulf, and eventual Atlantic Basin by the end of
the period. Organized convective activity will brew within the RER
of a strengthening upper jet core located over Ontario/Quebec as
the upper pattern becomes closed off to the west after 00z/Sun.
NAEFS PWAT anomalies between +1 and +2 deviations will offer a
suitable moisture rich environment conducive for stronger heavy
convective cores capable of locally enhanced rainfall prospects
within the confines of the great diffluent axis. As of this time,
this places the Appalachians Front from Northern GA up through PA
as the primary region of interest, however some elevated
instability notions are present within some of the recent
deterministic output. As of this time, a general 1-2" is forecast
within the above corridor with some heavier cells even possible as
far south as the Central Gulf Coast, but those are more aligned
within the decaying surface front that is progged to breakdown
before exiting the coastal plain. The area of focus will reside
within that broad ascent pattern enhanced by the evolving amplified
pattern to the east of the Mississippi with the complex terrain
providing a secondary element that would favor isolated flash flood
prospects. As a result, a broad MRGL risk extends from the
Southern Appalachians up through Northeast PA where the current
ensemble mean QPF is highest while also residing within the lower
FFG indices available in the Eastern CONUS.

...Great Basin...

Omega block pattern initiating over the CONUS will lead to yet
another amplified upper low generation across the Western CONUS
through D3. The threat for elevated convection in-of interior NV up
into Southeast OR have been forecast for several days with the
deterministic guidance basically "locked in" to the expected
evolution. Despite rainfall rates rather low grade compared to what
you normally find for flash flooding, this area has a notorious low
FFG bias that tends to accentuate the flash flood prospects in this
area of the CONUS. Recent ensemble means have been hovering between
0.75-1.25" of total QPF within the corridor extending from Reno to
points northeast with local maxima hovering up near 2" due to the
added effect of greater upper forcing thanks to the maturing closed
ULL reflection. This setup has been steady within the First Guess
Fields for the threat and really hasn't wavered much in the MRGL
risk output from the ML. Considering the factors above and a
pattern more favorable for these convective schemes across the
Great Basin, the previous MRGL risk inherited was maintained with a
small expansion northward into Southeast OR to highlight QPF trends
favoring better totals within those zones.

Kleebauer


Day 1 threat area: https://urldefense.com/v3/__https://www.wpc.ncep.noaa.gov/qpf/94epoints.txt= __;!!DZ3fjg!_AXeGXVYEr-vZZQ09Z3U33RrgGXMG0xI5KfwPAIK3iZ7jG13_u_A5_OT4JjNPKI= uJU8hrpZuC8XxAL9LWfCR1BL6jPo$=20
Day 2 threat area: https://urldefense.com/v3/__https://www.wpc.ncep.noaa.gov/qpf/98epoints.txt= __;!!DZ3fjg!_AXeGXVYEr-vZZQ09Z3U33RrgGXMG0xI5KfwPAIK3iZ7jG13_u_A5_OT4JjNPKI= uJU8hrpZuC8XxAL9LWfCRkUE_ABw$=20
Day 3 threat area: https://urldefense.com/v3/__https://www.wpc.ncep.noaa.gov/qpf/99epoints.txt= __;!!DZ3fjg!_AXeGXVYEr-vZZQ09Z3U33RrgGXMG0xI5KfwPAIK3iZ7jG13_u_A5_OT4JjNPKI= uJU8hrpZuC8XxAL9LWfCRxrzny5s$=20

=3D =3D =3D
To unsubscribe from WX-STORM and you already have a login, go to https://lists.illinois.edu and use the "Unsubscribe" link. Otherwise email Chris Novy at cnovy@cox.net and ask to be removed from WX-STORM.

--- SBBSecho 3.20-Linux
* Origin: capitolcityonline.net * Telnet/SSH:2022/HTTP (1:2320/105)

FOUS30 KWBC 020056
QPFERD

Excessive Rainfall Discussion
NWS Weather Prediction Center College Park MD
856 PM EDT Thu May 1 2025

Day 1
Valid 01Z Fri May 02 2025 - 12Z Fri May 02 2025

...THERE IS A SLIGHT RISK OF EXCESSIVE RAINFALL FOR SOUTHERN
OKLAHOMA AND FAR WESTERN ARKANSAS, SOUTH-CENTRAL TEXAS, AS WELL AS
FOR PORTIONS OF THE CENTRAL APPALACHIANS...

...01Z Update...

A Slight Risk was added to portions of south-central Texas, from=20
the U.S.-Mex border eastward through the Austin-San Antonio metros=20
to College Station, where slow-moving, heavy-rainfall producing=20
storms have increased in coverage this evening. Supported by moist, southeasterly low level inflow and high instability, some of these
storms have shown rainfall rates of 2-3 in/hr, with MRMS indicating=20 estimated totals of over 4 inches in the past 3 hours. There is=20
concern that conditions will remain favorable for continued=20
development, with the heavy rainfall threat persisting longer and=20
across a broader area than most of what the CAMs, including the=20
HRRR, indicate. Given the observed rainfall rates and the rainfall=20
already received in some areas, a Slight Risk was added. Refer to=20
WPC MPD #206 for additional details concerning the threat across=20
parts of this area.

Also added a Marginal Risk across portions of central and southern
California, where an upper level low interacting with PWs of
0.75-1 inch is supporting showers and thunderstorms, mostly along
the high terrain from the southern Sierra Nevada to the coastal
ranges, including the San Gabriel and Sierra Madre. Some of these
storms are producing torrential downpours and isolated flooding
concerns. Storms are expected to diminish later this evening, but
may pose additional concerns, especially across areas recently
impacted by wildfires.

Elsewhere, more minor adjustments were made to the previous outlook
based on current observations and CAM guidance.

Pereira

...16Z Update...

Only very minor tweaks were needed to the Slight Risk areas across
the Southern Plains and central Appalachians. For the southern
Plains, the 12Z HiRes guidance shifted very slightly (10-20 miles)
north with tonight's expected MCS development across Oklahoma.
Given the high sensitivity of that entire area between Dallas and
Oklahoma City for heavy rainfall, the Slight Risk was maintained.
The 12Z HRRR followed previous runs suggesting there may be
training showers that get hung up on the southern end of the MCS
just north of the Red River, but by then the instability should be
largely used up and therefore rates should come down a bit. Given
that, the Slight was maintained with no upgrades...though it
wouldn't take much of an uptick in future guidance to possibly need
a targeted Moderate, depending on if the guidance can come into
better agreement on where the axis of heaviest rain will set up.

Over to the Central Appalachians, the guidance unfortunately
remains in poorer agreement than in the southern Plains. Expect
more widely scattered convection to impact the area starting this
afternoon, developing into one or more lines of storms by the
evening. Each line will be very progressive/fast-moving, so
individual storms will not have much of a flooding impact. However,
with multiple rounds of showers and storms expected in an area
recently hard hit with heavy rain, the multiple rounds of storms
may collectively add up to widely scattered instances of flash
flooding into this evening. The inherited Slight was trimmed in
MD/WV out of areas east of the Allegheny Front, which are
significantly drier and with higher FFGs than areas along and west.

Wegman

...Previous Discussion...

...Southern Plains...

Shortwave ejection out of the Southern Rockies will interact with a
cold front pressing south through the Central and Southern Plains
by the late-afternoon and evening hours Thursday through Friday
morning. A relevant theta_E differential will be aligned within
the confines of the boundary providing a suitable thermodynamic
alignment such that area convection anchors and pushes along the
west to east oriented instability gradient across Southern OK.
Majority of CAMs are in consensus of a heavy rainfall footprint
along and south of I-40, generally configured to the timing of the
cold front, shortwave interaction, and LLJ convergence signal. This
is primarily right around 00z when the convective threat enhances
with the integration of the nocturnal LLJ, a timing historically
prevalent for this time of year and this setup is no exception.

00z HREF neighborhood probs for >1" are relatively high (50-80%)
within the corridor extending from Southwest OK across the Red
River Basin towards the AR border. >2" is highest just north of the
river from I-35 on east, a testament to the timing of the
shortwave arrival and upscale growth of the convective threat as it
maneuvers to the east-southeast. Rainfall rates between 1-2"/hr are
most likely when assessing the hourly rate probs from the both the
NBM and HREF output, a rate assessment that is more than suitable
considering the blanket low FFG intervals due to the antecedent
moist soils from the past 36-48 hrs of rainfall. The areal QPF
footprint of >1" aligned within those lower FFG's pretty much
perfectly, a scenario that lends to a greater credence of a touch
higher risk category that what is normal the case for this setup.
The previous SLGT risk was relatively maintained with minor
adjustments on the edges pertaining to recent hi-res QPF and in
conjunction with the ML First Guess Fields.

...Interior Mid Atlantic...

Shortwave trough currently positioned over the Southern Plains will
lift northeast through the Mississippi Valley with sights on the
Great Lakes region by the second half of the D1. Downstream, an
improved diffluent signature will align over the Ohio Valley and
points northeast allowing for regional ascent to boost convective
initiation in-of places within that diffluent core. The most
notable area for convective development lies within an established
theta_E tongue riding northward through the Appalachians Front
with poleward expansion into the southeastern Great Lakes. This
allowed for moisture rich air exuding PWAT anomalies between +2 and
+3 within the corridor extending through much of WV up through
Eastern OH and Western PA to the Lake Erie border. SBCAPE between
1500-2500 J/kg will be a common occurrence during peak diurnal
destabilization creating a corridor of enhanced thermodynamic
prospects to coincide with the arrival of the better mid-level
forcing downstream of the approaching trough. Regional shear will
be improving as well, especially within the confines of a shallow
warm front that will be lifting northward through the course of the
afternoon across the interior Mid Atlantic. Cell initiation will
begin between 18-00z today with greater multi-cell cluster coverage
likely to occur towards the back end of the above time frame due
to anchoring along the warm front as it approaches. Areas across
Western PA have been hit relatively hard recently with convective
rainfall adding to the areal decoupling of the FFG indices meaning
the prospects for flash flooding have increased with the arrival of
this next disturbance.

00z HREF neighborhood probs for >2" are between 30-50% across a
large section of Western PA extending south into the northern High
Country of WV, rooted in the Appalachians Front, an area notorious
for flashy rivers and smaller towns located within the valleys.
There was enough consensus to warrant an upgrade considering the
antecedent conditions, atmospheric environmental favorability, as
well as the increased probs denoting a locally heavy rain prospect
over the region. A SLGT risk has been added to much of Western PA
down into portions of the Central Appalachians.

Kleebauer


Day 2
Valid 12Z Fri May 02 2025 - 12Z Sat May 03 2025

...THERE IS A SLIGHT RISK OF EXCESSIVE RAINFALL ACROSS FROM THE
SOUTHERN PLAINS INTO THE LOWER MISSISSIPPI VALLEY...

...20Z Update...

A small southward nudge to the inherited Slight was added with this
update, with the Slight now including all of the upper Texas Gulf
Coast. A higher end Slight (not depicted) is in effect for the San
Antonio metro north and east, including the Houston Metro and into
northern and western Louisiana.

Overall very few changes were needed to the inherited risk areas.
The Slight Risk remains for much of Texas, from portions of the Rio
Grande Valley north and east to the Memphis metro. The heaviest
rains will be associated with a southward moving line of storms
with a cold front that will develop across central Texas Friday
afternoon and progress south and east to the Gulf Coast into Friday
night. Plentiful Gulf moisture ahead of the line with PWATs to 1.75
inches around the Houston metro and MUCAPE values well above 2,000
J/kg will favor very heavy rainfall rates with the strongest cores
of storms capable of over 2 inches per hour rain rates.
Fortunately, most of these areas of Texas have been drier than
areas to the north towards Oklahoma, so the lack of overlap with
previous rounds of heavy rain precluded the need for any Moderate
Risk upgrades this afternoon. There is some agreement in the
guidance that the heavy rain axis associated with the potential for
some limited training will remain just north of Houston in the Big
Thicket region. So long as this remains north of the most populated
areas around Houston then the Slight Risk should be sufficient, but
too much of a southward shift in that heavy rain axis would move
the threat into more urbanized areas, in which case a Moderate Risk
may be needed. 12Z HREF guidance shows an over 70% chance of 3
inches or more of rain in the neighborhood probabilities from just
west of the Louisiana border to Austin, remaining just north of
I-10.

The cold front driving these storms will advect much drier air into
much of Oklahoma and north Texas, which will greatly diminish any
storm threat in that area. For southeast Oklahoma, the threat is
largely Friday morning with lingering convection from the MCS that
will be progressing southeastward into northeast Texas and southern Arkansas/northern Louisiana.

Storms will be less organized and much faster moving progressing
northeast into the central Appalachians/western Pennsylvania. Thus,
despite low FFGs from recent heavy rains, the Marginal should
suffice for that area. Of course, should the storms slow down or
develop into multiple rounds, then a Slight will be needed.
Nonetheless, potential for heavy rains over saturated soils did
necessitate a small expansion of the Marginal to the southern Tier
of western New York.

Wegman

...Previous Discussion...

Steady progression of a cold front through the Southern Plains will
lead to textbook convergent pattern with an addition of a strong
upper diffluence signature within the bounds of the southern jet
proxy. High areal theta_E averages will denote the significant
instability pattern positioned ahead of the approaching cold front
leading to ample thermodynamic assistance for strong convective
cores and expected heavy rainfall. Recent CAMs have finally come
into view for the primary window of cell initiation with a
widespread convective pattern likely to extend from the Stockton
Plateau to points east within the I-10 corridor up through all of
Hill Country, especially over the I-35 section of south-central TX.
HREF blended mean QPF is over 2" now within a large area
encompassing the terrain focused across the Central portion of the
state. This had led to elevated neighborhood probs of >2" for the
12-00z time frame in the forecast running >70% over pretty much all
of the above region extending into portions of East TX. The East TX
corridor has become a newer development in terms of anticipated QPF
magnitude as the the CAMs and in some instances the global
deterministic are now catching on to the deep moisture advection
regime poking north out of the Western Gulf ahead of the front
arrival. Forecast soundings across the area between Houston up to
the latitude of Austin are now indicating MUCAPE or the order of
3500-5000 J/kg prior to any front arrival leading to significant
heavy cores to transpire due to cap breach from diurnal
destabilization initially, followed by more organized multi-cell
clusters as we move into the evening as the LLJ re-intensifies and
the cold front motions into the region.

Soundings also note a period of mean flow and upshear components
that would lead to potential backbuilding within the confines of
the front. Very strong ascent between 850-300mb is also noted
within multiple CAMs outputs, a testament to the favorability for
the setup to become more organized and providing a vast areal
expanse of heavy convection once the setup matures. PWATs between
1.6-1.9" with locally >2" are being forecast along and ahead of the
front as it moves into Central TX, a forecast that traditionally is
favored for greater flash flood prospects, especially over the
favored I-35 corridor between Austin to San Antonio where high
runoff capabilities are found due to soil type and limestone
foundations. Local totals between 3-6" are likely over the entire
stretch of Hill Country through East TX with the eastern most
extent even shifting into Western LA as the convective pattern
evolves and grows upscale entering into the adjacent Lower
Mississippi Valley. Houston metro is now in play for convective
impacts, especially as thunderstorms to the north provide outflow
generation that could send cold pools south towards the Gulf coast
with additional convective development along the edge of any
approaching cold pool.

The previous SLGT risk was relatively unchanged across Central TX.
Some expansion to the west was made into the Stockton Plateau where
initial cell formations will likely occur as the front arrives and
interacts with a formidable instability axis aligned over the
plateau itself. The SLGT was expanded southeast to cover the
Houston metro and points north where there is growing consensus on
convective impacts over and near the urban center. This is a high-
end SLGT over much of Central TX, especially Hill Country to the
I-35 corridor and points east. A risk upgrade is not out of the
question in subsequent updates given the environmental
favorability and flashy history of places expected to see the
greatest thunderstorm coverage/rates.

Kleebauer


Day 3
Valid 12Z Sat May 03 2025 - 12Z Sun May 04 2025

...THERE IS A MARGINAL RISK OF EXCESSIVE RAINFALL FROM THE CENTRAL
GULF COAST TO THE CENTRAL APPALACHIANS AS WELL AS PORTIONS OF THE
GREAT BASIN...

...20Z Update...

The inherited Marginal Risk was expanded south to the central Gulf
Coast with this update, with no changes towards the Great Basin.

Ongoing convection at the start of the period will impact the
central Gulf Coast on Saturday morning. While this area can take a
lot of rain before there are significant flooding issues, the
urbanization along the coast should support isolated instances of
flash flooding from New Orleans through Pensacola. Additional
afternoon convection will develop all throughout the Marginal Risk
area Saturday afternoon from the Gulf Coast through New York.
Topographic concerns and urban areas will be at higher risk for
potential flash flooding, but the otherwise progressive nature of
the storms should preclude more than isolated flash flooding in the
Marginal Risk area. PWATs over 1.5 inches from the Gulf Coast into
central Alabama and western Georgia would favor the most storms
capable of heavy rainfall. Depending on how much rainfall falls
along the Gulf Coast, especially through Mobile Friday night, the
additional rainfall Saturday could necessitate a Slight Risk
issuance with future updates from southern Alabama roughly to the
Atlanta area. Meanwhile further north once again the storms look to
be progressive enough that only isolated instances of flash
flooding are expected, including into western Pennsylvania.

Wegman

...Previous Discussion...

...Appalachians...

An anomalous upper low center evolving over the Ohio Valley will
generate a strong diffluent signature downstream across the
Appalachians and points east with a significant moisture fetch
poleward from the Gulf, and eventual Atlantic Basin by the end of
the period. Organized convective activity will brew within the RER
of a strengthening upper jet core located over Ontario/Quebec as
the upper pattern becomes closed off to the west after 00z/Sun.
NAEFS PWAT anomalies between +1 and +2 deviations will offer a
suitable moisture rich environment conducive for stronger heavy
convective cores capable of locally enhanced rainfall prospects
within the confines of the great diffluent axis. As of this time,
this places the Appalachians Front from Northern GA up through PA
as the primary region of interest, however some elevated
instability notions are present within some of the recent
deterministic output. As of this time, a general 1-2" is forecast
within the above corridor with some heavier cells even possible as
far south as the Central Gulf Coast, but those are more aligned
within the decaying surface front that is progged to breakdown
before exiting the coastal plain. The area of focus will reside
within that broad ascent pattern enhanced by the evolving amplified
pattern to the east of the Mississippi with the complex terrain
providing a secondary element that would favor isolated flash flood
prospects. As a result, a broad MRGL risk extends from the
Southern Appalachians up through Northeast PA where the current
ensemble mean QPF is highest while also residing within the lower
FFG indices available in the Eastern CONUS.

...Great Basin...

Omega block pattern initiating over the CONUS will lead to yet
another amplified upper low generation across the Western CONUS
through D3. The threat for elevated convection in-of interior NV up
into Southeast OR have been forecast for several days with the
deterministic guidance basically "locked in" to the expected
evolution. Despite rainfall rates rather low grade compared to what
you normally find for flash flooding, this area has a notorious low
FFG bias that tends to accentuate the flash flood prospects in this
area of the CONUS. Recent ensemble means have been hovering between
0.75-1.25" of total QPF within the corridor extending from Reno to
points northeast with local maxima hovering up near 2" due to the
added effect of greater upper forcing thanks to the maturing closed
ULL reflection. This setup has been steady within the First Guess
Fields for the threat and really hasn't wavered much in the MRGL
risk output from the ML. Considering the factors above and a
pattern more favorable for these convective schemes across the
Great Basin, the previous MRGL risk inherited was maintained with a
small expansion northward into Southeast OR to highlight QPF trends
favoring better totals within those zones.

Kleebauer


Day 1 threat area: https://urldefense.com/v3/__https://www.wpc.ncep.noaa.gov/qpf/94epoints.txt= __;!!DZ3fjg!-nP30Q989GMa3qmtki0qly0iHQZavlwcbwhYxmVu1k7Gk03DbpfCDvGaxtMgXOt= c0j5mCNCBZgNCwM0eXEw8CN2qaa4$=20
Day 2 threat area: https://urldefense.com/v3/__https://www.wpc.ncep.noaa.gov/qpf/98epoints.txt= __;!!DZ3fjg!-nP30Q989GMa3qmtki0qly0iHQZavlwcbwhYxmVu1k7Gk03DbpfCDvGaxtMgXOt= c0j5mCNCBZgNCwM0eXEw8L8M0qKY$=20
Day 3 threat area: https://urldefense.com/v3/__https://www.wpc.ncep.noaa.gov/qpf/99epoints.txt= __;!!DZ3fjg!-nP30Q989GMa3qmtki0qly0iHQZavlwcbwhYxmVu1k7Gk03DbpfCDvGaxtMgXOt= c0j5mCNCBZgNCwM0eXEw85hx6SF0$=20

=3D =3D =3D
To unsubscribe from WX-STORM and you already have a login, go to https://lists.illinois.edu and use the "Unsubscribe" link. Otherwise email Chris Novy at cnovy@cox.net and ask to be removed from WX-STORM.

--- SBBSecho 3.20-Linux
* Origin: capitolcityonline.net * Telnet/SSH:2022/HTTP (1:2320/105)

FOUS30 KWBC 020825
QPFERD

Excessive Rainfall Discussion
NWS Weather Prediction Center College Park MD
425 AM EDT Fri May 2 2025

Day 1
Valid 12Z Fri May 02 2025 - 12Z Sat May 03 2025

...THERE IS A SLIGHT RISK OF EXCESSIVE RAINFALL OVER PORTIONS OF
THE SOUTHERN PLAINS AND MID-SOUTH AND LOWER MISSISSIPPI...

Another round of thunderstorms is expected to develop along and
ahead of a southward moving cold front on Friday...with guidance
still focusing the greatest chances for excessive rainfall from
portions of the Mid-South into the Southern Plains Friday into
Friday night as weak waves propagate northeastward along the front.
Southerly low level flow will draw Gulf moisture northward...helping
increase precipitable water values ahead of the front to 1.5 to=20
1.75 inches at the time of the peak heating in a stripe from Texas=20
into southern Arkansas. Forecast soundings depict an atmosphere=20
supportive of rainfall rates exceeding 2 inches per hour. As=20
mentioned previously...the potential for a prolonged period of=20
training is fairly minimal so a Slight Risk still seems to cover=20
the potential. 00Z HREF neighborhood probabilities of 1-hour QPF
exceeding 2 inches were over 30 percent in parts of southeast TX
with lower probabilities extending into parts of Arkansas.

A Marginal Risk area surrounding the Slight Risk area extends as
far northeastward as parts of the Great Lakes. Precipitable water=20
values were generally at or below 1.25 inches ahead of the=20
advancing cold front but guidance still showed enough instability=20
to support showers and thunderstorms over an area that was still=20
had lingering hydrologic sensitivity following recent heavy=20
rainfall. In addition...the area will be underneath a right=20
entrance region of an upper level jet stream aiding upper level=20
support during the afternoon.=20

Farther west...there is also a Marginal risk of excessive rainfall
from late day and evening convection over the terrain of New
Mexico. The QPF is fairly modest but even modest rainfall rates
could result in isolated problems with run off...especially if the
rain falls on recent burn scars.

Bann

Day 2
Valid 12Z Sat May 03 2025 - 12Z Sun May 04 2025

....THERE IS A MARGINAL RISK OF EXCESSIVE RAINFALL FROM THE GULF
COAST REGION INTO PARTS OF THE EASTERN GREAT LAKES...

The focus for excessive rainfall will shift eastward as a closed
mid-level circulation center takes shape over the nation's mid-
section. The mid- and upper-level flow backs with time from the
Gulf coast northward across parts of the Tennessee and Ohio
Valleys. Initially...this allows deeper moisture to stream
northward. But it also results in the surface/low level front to
move eastward more quickly later in the period...with generally a=20
low-end risk of flooding from the Gulf coast northward. The 02/00Z=20
suite of numerical guidance hint that there could be some 1 inch to
perhaps 2 inch amounts where frontogenetic forcing aligns=20
favorably in between the Gulf and the Ohio Valley...but the signal=20
for excessive rainfall showed little run to run / model to model=20 consistency.

There is also a Marginal Risk of excessive rainfall over far
southern portion of Texas...where the southern end of the cold has
stalled its southward progression and return flow of Gulf moisture
has begun. Several of the High Res ensemble highlight this area=20
with QPF in the upper percentiles although the consensus is less=20
than unanimous in amounts or placement. With soundings showing=20
warm cloud processes through a deep layer and the CAPE profile is=20
tall and skinny...introduced a Marginal risk here.

Bann

Day 3
Valid 12Z Sun May 04 2025 - 12Z Mon May 05 2025

...THERE IS A MARGINAL RISK OF EXCESSIVE RAINFALL OVER PARTS OF THE
EASTERN UNITED STATES AND SOUTHERN ROCKIES ...

The risk of excessive rainfall persists across parts of the Mid-
Atlantic and Southeast US as a broad upper trough continues to make
its way eastward on Day 3. Deepest moisture of 1.25 to 1.5 inches
will be eventually be shunted off-shore late in the period. Until then...isolated downpours are possible with spaghetti plots of
2 and 3-inches of rain in 24 hours mainly being produced by models
with the ARW core...but enough members from the NMM core and from
the GEFS to warrant a Marginal.

There is also a Marginal Risk area over parts of New Mexico again
as moisture continue to spread northward and westward from the
Gulf. After 00Z...the flow aloft between the westerly subtropical
jet and a jet streak and low- and mid-levels become increasingly
diffluent with height falls beginning ahead of an approaching=20
closed low from the west. This...along with moisture and a low=20
level boundary already in place...should support late day and=20
evening storms that may produce locally heavy rainfall rates.

Bann


Day 1 threat area: https://urldefense.com/v3/__https://www.wpc.ncep.noaa.go= v/qpf/94epoints.txt__;!!DZ3fjg!8Se0ur8FErs805wBNmvpyvr1OpWoZfq9pUfSi5-fm4rs= h9JCwjDbZ0n96xW9uE8KdvYoVLPj6JLNVXNRHThj55UDT44$=20
Day 2 threat area: https://urldefense.com/v3/__https://www.wpc.ncep.noaa.go= v/qpf/98epoints.txt__;!!DZ3fjg!8Se0ur8FErs805wBNmvpyvr1OpWoZfq9pUfSi5-fm4rs= h9JCwjDbZ0n96xW9uE8KdvYoVLPj6JLNVXNRHThj5jK99Zw$=20
Day 3 threat area: https://urldefense.com/v3/__https://www.wpc.ncep.noaa.go= v/qpf/99epoints.txt__;!!DZ3fjg!8Se0ur8FErs805wBNmvpyvr1OpWoZfq9pUfSi5-fm4rs= h9JCwjDbZ0n96xW9uE8KdvYoVLPj6JLNVXNRHThjYlnzffo$=20

=3D =3D =3D
To unsubscribe from WX-STORM and you already have a login, go to https://lists.illinois.edu and use the "Unsubscribe" link. Otherwise email Chris Novy at cnovy@cox.net and ask to be removed from WX-STORM.

--- SBBSecho 3.20-Linux
* Origin: capitolcityonline.net * Telnet/SSH:2022/HTTP (1:2320/105)

FOUS30 KWBC 021551
QPFERD

Excessive Rainfall Discussion
NWS Weather Prediction Center College Park MD
1151 AM EDT Fri May 2 2025

Day 1
Valid 16Z Fri May 02 2025 - 12Z Sat May 03 2025

...THERE IS A SLIGHT RISK OF EXCESSIVE RAINFALL OVER PORTIONS OF
THE SOUTHERN PLAINS, LOWER MISSISSIPPI, AND TENNESSEE VALLEYS...

...16Z Update...

The most notable change with the midday update was to expand the
Slight eastward to include more of Tennessee and Alabama. The
Nashville, Chattanooga, and Birmingham metros are now upgraded to a Slight-risk, albeit a lower-end, lower confidence one.

Numerous areas of thunderstorms are expected to develop this
afternoon in response to growing instability and Gulf moisture
across the southern US ahead of a sweeping cold front. These storms
are forecast in the guidance to develop into several clusters. The
westernmost one over Texas will have the greatest potential to
cause flash flooding, as the southward push of the front is most
likely to stall out there as compared with areas further east.
Fortunately, once the current MCS over north Texas pushes further
south in response to new thunderstorm development this afternoon,
that should be the end of the heavy rain threat in that area for a
couple days. The best chance for training storms will generally be
from Austin east to roughly the Louisiana border, which has been
consistent in the guidance for at least the last 24 hours. Only a
small portion of this area was hit with heavy rain yesterday, and
with individual cells moving along with some southward component to
their motion, think the threat doesn't quite rise to the Moderate
Risk level, so the area remains in a Slight Risk.

Atmospheric ingredients remain favorable for the development of
flash flooding, with afternoon MUCAPE values expected to approach
3,000 J/kg across the Mid-South and PWATs in most areas between
1.25 and 1.5 inches. This is about 1-1.5 sigma above climatology
for this area. The PWATs will remain favorable as a 20-30 kt=20
southwesterly flow at 850 advects more Gulf moisture into the=20
storms that is lost from rainfall.

Thunderstorms will be a bit more progressive further east into
northern Louisiana and southern Arkansas, but that area has been
hard-hit with heavy rains over the past week, and soil moisture
levels remain quite high. Thus, with antecedent conditions more
favorable, the higher end Slight remains in effect for this area
with few changes.

Further east, as mentioned above the Slight Risk was expanded east
to include more of Alabama and Tennessee. The combination of urban
concerns in Nashville, Chattanooga, and Birmingham, some potential
for pre-line convection developing over those metros, and at or
above normal soil moisture levels in those areas favored the
upgrade to a lower-end Slight. The fast-moving progressive nature
of all of the storms, especially any line segments, does mitigate
the flash flood potential.

Finally, further up the front into the upper Ohio Valley and New
York, the storms will be moving even more quickly, with less Gulf
moisture to work with, but recent heavy rains in this area have
made antecedent soil moisture conditions very favorable for the
development of additional flash flooding, so the Marginal Risk area
was expanded northeastward, though the severe threat in this area
looks to be much greater.

No changes were made to the Marginal Risk across portions of
central and western New Mexico with few changes there in the
guidance.

Wegman

...Previous Discussion...

Another round of thunderstorms is expected to develop along and
ahead of a southward moving cold front on Friday...with guidance
still focusing the greatest chances for excessive rainfall from
portions of the Mid-South into the Southern Plains Friday into
Friday night as weak waves propagate northeastward along the front.
Southerly low level flow will draw Gulf moisture northward...helping
increase precipitable water values ahead of the front to 1.5 to
1.75 inches at the time of the peak heating in a stripe from Texas
into southern Arkansas. Forecast soundings depict an atmosphere
supportive of rainfall rates exceeding 2 inches per hour. As
mentioned previously...the potential for a prolonged period of
training is fairly minimal so a Slight Risk still seems to cover
the potential. 00Z HREF neighborhood probabilities of 1-hour QPF
exceeding 2 inches were over 30 percent in parts of southeast TX
with lower probabilities extending into parts of Arkansas.

A Marginal Risk area surrounding the Slight Risk area extends as
far northeastward as parts of the Great Lakes. Precipitable water
values were generally at or below 1.25 inches ahead of the
advancing cold front but guidance still showed enough instability
to support showers and thunderstorms over an area that was still
had lingering hydrologic sensitivity following recent heavy
rainfall. In addition...the area will be underneath a right
entrance region of an upper level jet stream aiding upper level
support during the afternoon.

Farther west...there is also a Marginal risk of excessive rainfall
from late day and evening convection over the terrain of New
Mexico. The QPF is fairly modest but even modest rainfall rates
could result in isolated problems with run off...especially if the
rain falls on recent burn scars.

Bann

Day 2
Valid 12Z Sat May 03 2025 - 12Z Sun May 04 2025

....THERE IS A MARGINAL RISK OF EXCESSIVE RAINFALL FROM THE GULF
COAST REGION INTO PARTS OF THE EASTERN GREAT LAKES...

The focus for excessive rainfall will shift eastward as a closed
mid-level circulation center takes shape over the nation's mid-
section. The mid- and upper-level flow backs with time from the
Gulf coast northward across parts of the Tennessee and Ohio
Valleys. Initially...this allows deeper moisture to stream
northward. But it also results in the surface/low level front to
move eastward more quickly later in the period...with generally a
low-end risk of flooding from the Gulf coast northward. The 02/00Z
suite of numerical guidance hint that there could be some 1 inch to
perhaps 2 inch amounts where frontogenetic forcing aligns
favorably in between the Gulf and the Ohio Valley...but the signal
for excessive rainfall showed little run to run / model to model
consistency.

There is also a Marginal Risk of excessive rainfall over far
southern portion of Texas...where the southern end of the cold has
stalled its southward progression and return flow of Gulf moisture
has begun. Several of the High Res ensemble highlight this area
with QPF in the upper percentiles although the consensus is less
than unanimous in amounts or placement. With soundings showing
warm cloud processes through a deep layer and the CAPE profile is
tall and skinny...introduced a Marginal risk here.

Bann

Day 3
Valid 12Z Sun May 04 2025 - 12Z Mon May 05 2025

...THERE IS A MARGINAL RISK OF EXCESSIVE RAINFALL OVER PARTS OF THE
EASTERN UNITED STATES AND SOUTHERN ROCKIES ...

The risk of excessive rainfall persists across parts of the Mid-
Atlantic and Southeast US as a broad upper trough continues to make
its way eastward on Day 3. Deepest moisture of 1.25 to 1.5 inches
will be eventually be shunted off-shore late in the period. Until then...isolated downpours are possible with spaghetti plots of
2 and 3-inches of rain in 24 hours mainly being produced by models
with the ARW core...but enough members from the NMM core and from
the GEFS to warrant a Marginal.

There is also a Marginal Risk area over parts of New Mexico again
as moisture continue to spread northward and westward from the
Gulf. After 00Z...the flow aloft between the westerly subtropical
jet and a jet streak and low- and mid-levels become increasingly
diffluent with height falls beginning ahead of an approaching
closed low from the west. This...along with moisture and a low
level boundary already in place...should support late day and
evening storms that may produce locally heavy rainfall rates.

Bann


Day 1 threat area: https://urldefense.com/v3/__https://www.wpc.ncep.noaa.go= v/qpf/94epoints.txt__;!!DZ3fjg!6Zq6E6KYIAsErfHvCj-V_vwbM4OhwNlyWxzjTEfImoV2= Zx41mNloEXwH2hkhpYW_fwAFMeyMQCN49jYbXLZBfVaCZ5Y$=20
Day 2 threat area: https://urldefense.com/v3/__https://www.wpc.ncep.noaa.go= v/qpf/98epoints.txt__;!!DZ3fjg!6Zq6E6KYIAsErfHvCj-V_vwbM4OhwNlyWxzjTEfImoV2= Zx41mNloEXwH2hkhpYW_fwAFMeyMQCN49jYbXLZBWnEfy2s$=20
Day 3 threat area: https://urldefense.com/v3/__https://www.wpc.ncep.noaa.go= v/qpf/99epoints.txt__;!!DZ3fjg!6Zq6E6KYIAsErfHvCj-V_vwbM4OhwNlyWxzjTEfImoV2= Zx41mNloEXwH2hkhpYW_fwAFMeyMQCN49jYbXLZBxUwaILM$=20

=3D =3D =3D
To unsubscribe from WX-STORM and you already have a login, go to https://lists.illinois.edu and use the "Unsubscribe" link. Otherwise email Chris Novy at cnovy@cox.net and ask to be removed from WX-STORM.

--- SBBSecho 3.20-Linux
* Origin: capitolcityonline.net * Telnet/SSH:2022/HTTP (1:2320/105)

FOUS30 KWBC 022000
QPFERD

Excessive Rainfall Discussion
NWS Weather Prediction Center College Park MD
400 PM EDT Fri May 2 2025

Day 1
Valid 16Z Fri May 02 2025 - 12Z Sat May 03 2025

...THERE IS A SLIGHT RISK OF EXCESSIVE RAINFALL OVER PORTIONS OF
THE SOUTHERN PLAINS, LOWER MISSISSIPPI, AND TENNESSEE VALLEYS...

...16Z Update...

The most notable change with the midday update was to expand the
Slight eastward to include more of Tennessee and Alabama. The
Nashville, Chattanooga, and Birmingham metros are now upgraded to a Slight-risk, albeit a lower-end, lower confidence one.

Numerous areas of thunderstorms are expected to develop this
afternoon in response to growing instability and Gulf moisture
across the southern US ahead of a sweeping cold front. These storms
are forecast in the guidance to develop into several clusters. The
westernmost one over Texas will have the greatest potential to
cause flash flooding, as the southward push of the front is most
likely to stall out there as compared with areas further east.
Fortunately, once the current MCS over north Texas pushes further
south in response to new thunderstorm development this afternoon,
that should be the end of the heavy rain threat in that area for a
couple days. The best chance for training storms will generally be
from Austin east to roughly the Louisiana border, which has been
consistent in the guidance for at least the last 24 hours. Only a
small portion of this area was hit with heavy rain yesterday, and
with individual cells moving along with some southward component to
their motion, think the threat doesn't quite rise to the Moderate
Risk level, so the area remains in a Slight Risk.

Atmospheric ingredients remain favorable for the development of
flash flooding, with afternoon MUCAPE values expected to approach
3,000 J/kg across the Mid-South and PWATs in most areas between
1.25 and 1.5 inches. This is about 1-1.5 sigma above climatology
for this area. The PWATs will remain favorable as a 20-30 kt
southwesterly flow at 850 advects more Gulf moisture into the
storms that is lost from rainfall.

Thunderstorms will be a bit more progressive further east into
northern Louisiana and southern Arkansas, but that area has been
hard-hit with heavy rains over the past week, and soil moisture
levels remain quite high. Thus, with antecedent conditions more
favorable, the higher end Slight remains in effect for this area
with few changes.

Further east, as mentioned above the Slight Risk was expanded east
to include more of Alabama and Tennessee. The combination of urban
concerns in Nashville, Chattanooga, and Birmingham, some potential
for pre-line convection developing over those metros, and at or
above normal soil moisture levels in those areas favored the
upgrade to a lower-end Slight. The fast-moving progressive nature
of all of the storms, especially any line segments, does mitigate
the flash flood potential.

Finally, further up the front into the upper Ohio Valley and New
York, the storms will be moving even more quickly, with less Gulf
moisture to work with, but recent heavy rains in this area have
made antecedent soil moisture conditions very favorable for the
development of additional flash flooding, so the Marginal Risk area
was expanded northeastward, though the severe threat in this area
looks to be much greater.

No changes were made to the Marginal Risk across portions of
central and western New Mexico with few changes there in the
guidance.

Wegman

...Previous Discussion...

Another round of thunderstorms is expected to develop along and
ahead of a southward moving cold front on Friday...with guidance
still focusing the greatest chances for excessive rainfall from
portions of the Mid-South into the Southern Plains Friday into
Friday night as weak waves propagate northeastward along the front.
Southerly low level flow will draw Gulf moisture northward...helping
increase precipitable water values ahead of the front to 1.5 to
1.75 inches at the time of the peak heating in a stripe from Texas
into southern Arkansas. Forecast soundings depict an atmosphere
supportive of rainfall rates exceeding 2 inches per hour. As
mentioned previously...the potential for a prolonged period of
training is fairly minimal so a Slight Risk still seems to cover
the potential. 00Z HREF neighborhood probabilities of 1-hour QPF
exceeding 2 inches were over 30 percent in parts of southeast TX
with lower probabilities extending into parts of Arkansas.

A Marginal Risk area surrounding the Slight Risk area extends as
far northeastward as parts of the Great Lakes. Precipitable water
values were generally at or below 1.25 inches ahead of the
advancing cold front but guidance still showed enough instability
to support showers and thunderstorms over an area that was still
had lingering hydrologic sensitivity following recent heavy
rainfall. In addition...the area will be underneath a right
entrance region of an upper level jet stream aiding upper level
support during the afternoon.

Farther west...there is also a Marginal risk of excessive rainfall
from late day and evening convection over the terrain of New
Mexico. The QPF is fairly modest but even modest rainfall rates
could result in isolated problems with run off...especially if the
rain falls on recent burn scars.

Bann

Day 2
Valid 12Z Sat May 03 2025 - 12Z Sun May 04 2025

....THERE IS A MARGINAL RISK OF EXCESSIVE RAINFALL FROM THE GULF
COAST REGION INTO PARTS OF THE NORTHEAST, EXTREME DEEP SOUTH TEXAS,
AND THE SACRAMENTO MOUNTAINS OF NEW MEXICO...

...20Z Update...

The Marginal Risk across portions of the East Coast was expanded
east to include portions of the I-95 corridor through DC and
Baltimore, the Piedmont of the Carolinas, and expanded west into
east central Illinois. A new Marginal Risk was issued for the
Sacramento Mountains of New Mexico.

Due to uncertainties with potential training storms up the Blue
Ridge of VA into PA, including impacts into the DC and Baltimore
metros, a low-end Marginal expanded to include that portion of the
I-95 corridor with this update. Most of the guidance suggests any
heavier rains and training storms will be west of the metro, and
the ongoing severe drought will mitigate most impacts, but an
isolated flood can't be ruled out should training storms move over
those cities. Given some instability expected into southern New
England, the Marginal was also expanded into western MA and CT on
the assumption that northeastward moving storms may persist longer
into New England. Wraparound rain around the north side of a cutoff
low over Illinois has resulted in a decently well agreed upon
maximum of rainfall into east central Illinois, so the Marginal was
expanded west for that as well.

The Marginal in extreme deep south Texas was trimmed from the north
to exclude areas with very high FFGs. It appears increasingly
likely that the storms impacting that area, if they train, will be
south of the border, but some potential remains into McAllen and
Brownsville for training storms, so the Marginal was left in place
for those urban centers.

In coordination with ABQ/Albuquerque WFO, a Marginal was introduced
for the Sacramento Mountains for the potential for nearly
stationary storms tied to the terrain impacting old burn scar areas
near Ruidoso, NM.=20=20

Wegman

...Previous Discussion...

The focus for excessive rainfall will shift eastward as a closed
mid-level circulation center takes shape over the nation's mid-
section. The mid- and upper-level flow backs with time from the
Gulf coast northward across parts of the Tennessee and Ohio
Valleys. Initially...this allows deeper moisture to stream
northward. But it also results in the surface/low level front to
move eastward more quickly later in the period...with generally a
low-end risk of flooding from the Gulf coast northward. The 02/00Z
suite of numerical guidance hint that there could be some 1 inch to
perhaps 2 inch amounts where frontogenetic forcing aligns
favorably in between the Gulf and the Ohio Valley...but the signal
for excessive rainfall showed little run to run / model to model
consistency.

There is also a Marginal Risk of excessive rainfall over far
southern portion of Texas...where the southern end of the cold has
stalled its southward progression and return flow of Gulf moisture
has begun. Several of the High Res ensemble highlight this area
with QPF in the upper percentiles although the consensus is less
than unanimous in amounts or placement. With soundings showing
warm cloud processes through a deep layer and the CAPE profile is
tall and skinny...introduced a Marginal risk here.

Bann

Day 3
Valid 12Z Sun May 04 2025 - 12Z Mon May 05 2025

...THERE IS A MARGINAL RISK OF EXCESSIVE RAINFALL OVER PARTS OF THE
EASTERN UNITED STATES AND SOUTHERN ROCKIES ...

...20Z Update...

The Marginal Risk across the East Coast was expanded greatly to
include much of the Northeast, Mid-Atlantic and coastal Carolinas,
with the other Marginal expanded well west to include portions of
southwest Colorado, southern Utah, and eastern Nevada with this
update.

The Marginal across the east will be for continue training showers
and storms into New England, with a maximum of rainfall likely near
the Catskills and Poconos of NY and PA, respectively. Rates should
remain low enough with some breaks in the rain that amounts remain
within Marginal thresholds, but should the Day 2/Saturday rainfall
overperform in this area or if the forecast rain comes up for
Sunday, then a targeted Slight risk may be needed. Occasional
storms with MUCAPE instability values between 500 and 1,000 J/kg
are more likely to impact more of the I-95 corridor from Raleigh,
NC through NYC. Drought conditions are very likely to temper all
but the most persistent rains, but given the sensitivities in the
urban corridor, the Marginal was expanded to account for potential
training storms.

The Marginal Risk out west was expanded with a deep but slow moving
upper level low and trough moving across the 4-corners region,
drawing some Gulf moisture well northwest and into the area, where
terrain will cause localized upslope. Rocky terrain will also favor
rapid development of flash flooding in the local areas where the
rain is most persistent. The highest elevations will see mostly
snow from this event, but most of the area should see rain, which
is the rationale for the expansion of the Marginal. The San Juans
will have some of the heaviest precipitation, which should lower
snow levels locally enough to carve that area out of the Marginal
with this update.

Wegman

...Previous Discussion...

The risk of excessive rainfall persists across parts of the Mid-
Atlantic and Southeast US as a broad upper trough continues to make
its way eastward on Day 3. Deepest moisture of 1.25 to 1.5 inches
will be eventually be shunted off-shore late in the period. Until then...isolated downpours are possible with spaghetti plots of
2 and 3-inches of rain in 24 hours mainly being produced by models
with the ARW core...but enough members from the NMM core and from
the GEFS to warrant a Marginal.

There is also a Marginal Risk area over parts of New Mexico again
as moisture continue to spread northward and westward from the
Gulf. After 00Z...the flow aloft between the westerly subtropical
jet and a jet streak and low- and mid-levels become increasingly
diffluent with height falls beginning ahead of an approaching
closed low from the west. This...along with moisture and a low
level boundary already in place...should support late day and
evening storms that may produce locally heavy rainfall rates.

Bann


Day 1 threat area: https://urldefense.com/v3/__https://www.wpc.ncep.noaa.go= v/qpf/94epoints.txt__;!!DZ3fjg!67oFAOdrDstnwlQclUaUZKyykGGcgqjaVa3ERZigDsW9= LzYavGn_3WsWyynCpgGsEMAbB06_ehrmtlSSQrKcQ5qADyc$=20
Day 2 threat area: https://urldefense.com/v3/__https://www.wpc.ncep.noaa.go= v/qpf/98epoints.txt__;!!DZ3fjg!67oFAOdrDstnwlQclUaUZKyykGGcgqjaVa3ERZigDsW9= LzYavGn_3WsWyynCpgGsEMAbB06_ehrmtlSSQrKcQQ1t4_k$=20
Day 3 threat area: https://urldefense.com/v3/__https://www.wpc.ncep.noaa.go= v/qpf/99epoints.txt__;!!DZ3fjg!67oFAOdrDstnwlQclUaUZKyykGGcgqjaVa3ERZigDsW9= LzYavGn_3WsWyynCpgGsEMAbB06_ehrmtlSSQrKcjk_OGw4$=20

=3D =3D =3D
To unsubscribe from WX-STORM and you already have a login, go to https://lists.illinois.edu and use the "Unsubscribe" link. Otherwise email Chris Novy at cnovy@cox.net and ask to be removed from WX-STORM.

--- SBBSecho 3.20-Linux
* Origin: capitolcityonline.net * Telnet/SSH:2022/HTTP (1:2320/105)

FOUS30 KWBC 030100
QPFERD

Excessive Rainfall Discussion
NWS Weather Prediction Center College Park MD
900 PM EDT Fri May 2 2025

Day 1
Valid 01Z Sat May 03 2025 - 12Z Sat May 03 2025

...THERE IS A SLIGHT RISK OF EXCESSIVE RAINFALL OVER PORTIONS OF
THE SOUTHERN PLAINS, LOWER MISSISSIPPI, TO THE SOUTHERN
APPALACHIANS...

01Z Update...

Biggest adjustment to the previous outlook was to trim away the
northwestern extent of the previous outlooks across northern Texas=20
where the heavy rain and flooding threat has ended and where=20
additional development is not expected.

A Slight Risk remains in place from Southwest through South-
Central Texas into Southwest Louisiana where locally heavy showers=20
will continue through the evening hours -- producing additional=20
areas of flash flooding. Refer to WPC MPD #212 for additional=20
information regarding the near-term heavy rain and flooding threat=20
across this area.

Further to the east, extended the previous Slight Risk area south
into parts of southeastern Louisiana, southern Mississippi,=20
Alabama, and the far western Florida Panhandle. Recent runs of the=20
HRRR and some of the other CAM guidance show slow-moving convection
developing later this evening along an axis of enhanced=20
convergence near the coast, with possible mergers with the upstream
convection now moving across the lower Mississippi Valley. The 18Z
HREF shows high neighborhood probabilities for evening/overnight=20 accumulations exceeding 3 inches centered near Mobile Bay.

Similar to areas back to the west, the Slight Risk was trimmed out
of the Tennessee Valley where the rainfall has ended. A Slight=20
Risk was maintained from central Alabama northeastward into the=20
southern Applachians where convection continues to develop and move
ahead of an upstream front.
=20
Pereira

Day 2
Valid 12Z Sat May 03 2025 - 12Z Sun May 04 2025

....THERE IS A MARGINAL RISK OF EXCESSIVE RAINFALL FROM THE GULF
COAST REGION INTO PARTS OF THE NORTHEAST, EXTREME DEEP SOUTH TEXAS,
AND THE SACRAMENTO MOUNTAINS OF NEW MEXICO...

...20Z Update...

The Marginal Risk across portions of the East Coast was expanded
east to include portions of the I-95 corridor through DC and
Baltimore, the Piedmont of the Carolinas, and expanded west into
east central Illinois. A new Marginal Risk was issued for the
Sacramento Mountains of New Mexico.

Due to uncertainties with potential training storms up the Blue
Ridge of VA into PA, including impacts into the DC and Baltimore
metros, a low-end Marginal expanded to include that portion of the
I-95 corridor with this update. Most of the guidance suggests any
heavier rains and training storms will be west of the metro, and
the ongoing severe drought will mitigate most impacts, but an
isolated flood can't be ruled out should training storms move over
those cities. Given some instability expected into southern New
England, the Marginal was also expanded into western MA and CT on
the assumption that northeastward moving storms may persist longer
into New England. Wraparound rain around the north side of a cutoff
low over Illinois has resulted in a decently well agreed upon
maximum of rainfall into east central Illinois, so the Marginal was
expanded west for that as well.

The Marginal in extreme deep south Texas was trimmed from the north
to exclude areas with very high FFGs. It appears increasingly
likely that the storms impacting that area, if they train, will be
south of the border, but some potential remains into McAllen and
Brownsville for training storms, so the Marginal was left in place
for those urban centers.

In coordination with ABQ/Albuquerque WFO, a Marginal was introduced
for the Sacramento Mountains for the potential for nearly
stationary storms tied to the terrain impacting old burn scar areas
near Ruidoso, NM.

Wegman

...Previous Discussion...

The focus for excessive rainfall will shift eastward as a closed
mid-level circulation center takes shape over the nation's mid-
section. The mid- and upper-level flow backs with time from the
Gulf coast northward across parts of the Tennessee and Ohio
Valleys. Initially...this allows deeper moisture to stream
northward. But it also results in the surface/low level front to
move eastward more quickly later in the period...with generally a
low-end risk of flooding from the Gulf coast northward. The 02/00Z
suite of numerical guidance hint that there could be some 1 inch to
perhaps 2 inch amounts where frontogenetic forcing aligns
favorably in between the Gulf and the Ohio Valley...but the signal
for excessive rainfall showed little run to run / model to model
consistency.

There is also a Marginal Risk of excessive rainfall over far
southern portion of Texas...where the southern end of the cold has
stalled its southward progression and return flow of Gulf moisture
has begun. Several of the High Res ensemble highlight this area
with QPF in the upper percentiles although the consensus is less
than unanimous in amounts or placement. With soundings showing
warm cloud processes through a deep layer and the CAPE profile is
tall and skinny...introduced a Marginal risk here.

Bann

Day 3
Valid 12Z Sun May 04 2025 - 12Z Mon May 05 2025

...THERE IS A MARGINAL RISK OF EXCESSIVE RAINFALL OVER PARTS OF THE
EASTERN UNITED STATES AND SOUTHERN ROCKIES ...

...20Z Update...

The Marginal Risk across the East Coast was expanded greatly to
include much of the Northeast, Mid-Atlantic and coastal Carolinas,
with the other Marginal expanded well west to include portions of
southwest Colorado, southern Utah, and eastern Nevada with this
update.

The Marginal across the east will be for continue training showers
and storms into New England, with a maximum of rainfall likely near
the Catskills and Poconos of NY and PA, respectively. Rates should
remain low enough with some breaks in the rain that amounts remain
within Marginal thresholds, but should the Day 2/Saturday rainfall
overperform in this area or if the forecast rain comes up for
Sunday, then a targeted Slight risk may be needed. Occasional
storms with MUCAPE instability values between 500 and 1,000 J/kg
are more likely to impact more of the I-95 corridor from Raleigh,
NC through NYC. Drought conditions are very likely to temper all
but the most persistent rains, but given the sensitivities in the
urban corridor, the Marginal was expanded to account for potential
training storms.

The Marginal Risk out west was expanded with a deep but slow moving
upper level low and trough moving across the 4-corners region,
drawing some Gulf moisture well northwest and into the area, where
terrain will cause localized upslope. Rocky terrain will also favor
rapid development of flash flooding in the local areas where the
rain is most persistent. The highest elevations will see mostly
snow from this event, but most of the area should see rain, which
is the rationale for the expansion of the Marginal. The San Juans
will have some of the heaviest precipitation, which should lower
snow levels locally enough to carve that area out of the Marginal
with this update.

Wegman

...Previous Discussion...

The risk of excessive rainfall persists across parts of the Mid-
Atlantic and Southeast US as a broad upper trough continues to make
its way eastward on Day 3. Deepest moisture of 1.25 to 1.5 inches
will be eventually be shunted off-shore late in the period. Until then...isolated downpours are possible with spaghetti plots of
2 and 3-inches of rain in 24 hours mainly being produced by models
with the ARW core...but enough members from the NMM core and from
the GEFS to warrant a Marginal.

There is also a Marginal Risk area over parts of New Mexico again
as moisture continue to spread northward and westward from the
Gulf. After 00Z...the flow aloft between the westerly subtropical
jet and a jet streak and low- and mid-levels become increasingly
diffluent with height falls beginning ahead of an approaching
closed low from the west. This...along with moisture and a low
level boundary already in place...should support late day and
evening storms that may produce locally heavy rainfall rates.

Bann


Day 1 threat area: https://urldefense.com/v3/__https://www.wpc.ncep.noaa.go= v/qpf/94epoints.txt__;!!DZ3fjg!81qhY1qFl3jBHGcMIsZVaTePDhnpfLJ1QJevNXchGRYF= cE9wf8Lz-4_tamSGOqTVUVK8YlWGJ0NqaqezhI_fv9xoAvQ$=20
Day 2 threat area: https://urldefense.com/v3/__https://www.wpc.ncep.noaa.go= v/qpf/98epoints.txt__;!!DZ3fjg!81qhY1qFl3jBHGcMIsZVaTePDhnpfLJ1QJevNXchGRYF= cE9wf8Lz-4_tamSGOqTVUVK8YlWGJ0NqaqezhI_fPaP7DdI$=20
Day 3 threat area: https://urldefense.com/v3/__https://www.wpc.ncep.noaa.go= v/qpf/99epoints.txt__;!!DZ3fjg!81qhY1qFl3jBHGcMIsZVaTePDhnpfLJ1QJevNXchGRYF= cE9wf8Lz-4_tamSGOqTVUVK8YlWGJ0NqaqezhI_fhomXhaA$=20

=3D =3D =3D
To unsubscribe from WX-STORM and you already have a login, go to https://lists.illinois.edu and use the "Unsubscribe" link. Otherwise email Chris Novy at cnovy@cox.net and ask to be removed from WX-STORM.

--- SBBSecho 3.20-Linux
* Origin: capitolcityonline.net * Telnet/SSH:2022/HTTP (1:2320/105)

FOUS30 KWBC 030828
QPFERD

Excessive Rainfall Discussion
NWS Weather Prediction Center College Park MD
428 AM EDT Sat May 3 2025

Day 1
Valid 12Z Sat May 03 2025 - 12Z Sun May 04 2025

...THERE IS A MARGINAL RISK OF EXCESSIVE RAINFALL FROM THE GULF
COAST REGION INTO PARTS OF THE NORTHEAST AND THE SACRAMENTO=20
MOUNTAINS OF NEW MEXICO

A slow moving mid- and upper-level circulation is expected to form
later today within a broader mid/upper level trough digging
eastward. With low level flow drawing deeper moisture northward
ahead of the system...thunderstorms that form along and immediately
east of a surface cold front will be moving into an environment of
supporting locally heavy rainfall rates and amounts over portions
of the Ohio Valley southward towards the Gulf coast today and from
portions of southern New England southward towards the Carolinas
and areas in and near the southern Appalachians where deeper
moisture resides this afternoon and evening, The 03/00Z suite of=20
numerical guidance hint that there could be some 1 inch to perhaps=20
2 inch amounts where frontogenetic forcing aligns favorably in=20
between the Gulf and the Ohio Valley...but the signal for excessive
rainfall appeared tempered by the progressive nature of the=20
forcing and confidence was limited by the lack of run to run /=20
model to model consistency with placement of highest model QPF.

Maintained the previously issued Marginal Risk area in New Mexico
given the antecedent conditions after the rain on Friday and the
sensitivity over/near burn scars in the southeast portion of the
state.


Bann

Day 2
Valid 12Z Sun May 04 2025 - 12Z Mon May 05 2025

...THERE IS A MARGINAL RISK OF EXCESSIVE RAINFALL OVER PARTS OF THE
EASTERN UNITED STATES AND SOUTHERN ROCKIES AND ADJACENT HIGH PLAINS...

The risk of excessive rainfall persists across parts of the Mid-
Atlantic and Southeast US as a slow moving closed low embedded=20
within a broader upper trough continues to make its way eastward. Deepest moisture of 1.25 to 1.5 inches will be eventually be shunted off-=20
shore late in the period. Until then...isolated downpours are=20
possible with spaghetti plots of 2 and 3-inches of rain in 24 hours
mainly being produced by models with the ARW core...but enough=20
members from the NMM core and from the GEFS to warrant a Marginal.
The western boundary of the Marginal was trimmed compared with the
previous outlook given the models being more progressive with the
surface cold front and the push of drier air being brought in
behind the front.

There is also a Marginal Risk area over parts of New Mexico again
as moisture continue to spread northward and westward from the
Gulf. After 00Z...the flow aloft between the westerly subtropical
jet and a jet streak and low- and mid-levels become increasingly
diffluent with height falls beginning ahead of an approaching
closed low from the west. This...along with moisture and a low
level boundary already in place...should support late day and
evening storms that may produce locally heavy rainfall rates.


Bann

Day 3
Valid 12Z Mon May 05 2025 - 12Z Tue May 06 2025

...THERE IS A SLIGHT RISK OF EXCESSIVE RAINFALL OVER PORTIONS OF
THE HIGH PLAINS ADJACENT TO THE SOUTHERN ROCKIES...

Shortwave energy rotating around the periphery of an upper low
making its way over the Southwest US will trigger late day
thunderstorms on Monday over parts of West Texas that grow upscale
in terms of both coverage and rainfall amounts through much of
Monday night/early Tuesday morning. A feed of low level moisture
being forced upslope ahead of the approaching shortwave will help
fuel the potential for downpours and locally heavy rainfall amounts
leading to the potential of flash flooding. QPF from the
operational models have maximum amounts of rainfall in the 2.5 to
3.8 inches...which tended to be supported by the SREF and GEFS
spaghetti plots and by machine learning first guess EROs. Felt a
Slight Risk area covers the potential for time being.

Bann


Day 1 threat area: https://urldefense.com/v3/__https://www.wpc.ncep.noaa.go= v/qpf/94epoints.txt__;!!DZ3fjg!5GiQRjXI-zhvsbjJchraKR0RNACTqP7KZrpWzR27utmb= ABVDhrd0SaEAadKRLbTXGH6wSiRM-HfKGfMqAms0NqJqglY$=20
Day 2 threat area: https://urldefense.com/v3/__https://www.wpc.ncep.noaa.go= v/qpf/98epoints.txt__;!!DZ3fjg!5GiQRjXI-zhvsbjJchraKR0RNACTqP7KZrpWzR27utmb= ABVDhrd0SaEAadKRLbTXGH6wSiRM-HfKGfMqAms0c6DUwbo$=20
Day 3 threat area: https://urldefense.com/v3/__https://www.wpc.ncep.noaa.go= v/qpf/99epoints.txt__;!!DZ3fjg!5GiQRjXI-zhvsbjJchraKR0RNACTqP7KZrpWzR27utmb= ABVDhrd0SaEAadKRLbTXGH6wSiRM-HfKGfMqAms0OD249FA$=20

=3D =3D =3D
To unsubscribe from WX-STORM and you already have a login, go to https://lists.illinois.edu and use the "Unsubscribe" link. Otherwise email Chris Novy at cnovy@cox.net and ask to be removed from WX-STORM.

--- SBBSecho 3.20-Linux
* Origin: capitolcityonline.net * Telnet/SSH:2022/HTTP (1:2320/105)

FOUS30 KWBC 031559
QPFERD

Excessive Rainfall Discussion
NWS Weather Prediction Center College Park MD
1159 AM EDT Sat May 3 2025

Day 1
Valid 16Z Sat May 03 2025 - 12Z Sun May 04 2025

...THERE IS A MARGINAL RISK OF EXCESSIVE RAINFALL FOR MUCH OF THE
EASTERN U.S. AND THE SACRAMENTO MOUNTAINS OF NEW MEXICO...

16Z Update...=20
An upper-level low is forming over the mid-Mississippi region and=20
becomes cutoff over Kentucky tonight as the jet focuses over=20
eastern Canada. Low level flow is drawing Gulf moisture through and
ahead of the system from the Gulf Coast up through the Eastern=20
Seaboard. Several focus areas for thunderstorms are expected=20
through tonight in the broad area which covered by a contiguous=20
Marginal Risk.=20

Ohio Valley to Gulf Coast...=20
Locally heavy activity has developed ahead of a surface low over=20
western TN with scattered storms south ahead of the advancing cold=20
front through MS and north along a stalled boundary that extends to
the upper Ohio Valley. This activity may pivot over eastern=20
KY/southern OH through the middle afternoon while activity over AL=20
to the Gulf Coast should be more progressive.=20

Carolinas, Central Appalachians and Mid-Atlantic...=20
Lee trough development over the Piedmont in the Carolinas later=20
this afternoon will allow potentially training activity in deep=20
SSWly flow there well into the evening, so the Marginal Risk was=20
expanded east a bit over SC/NC. This activity lifts north through
the central Appalachians into this evening with localized flash
flood threats. Later tonight the activity shifts east with some
training potential, so the Marginal was maintained east through the Baltimore/Washington urban centers.


Northeast...
The northern end of the moisture plume converges on a frontal zone
over Upstate NY and central New England through this afternoon=20
bringing potential for excessive rain despite strong deep layer=20
flow. The Marginal Risk was expanded north into central New=20
England. A second round of development is expected farther south=20
this evening in the Hudson Valley and southern New England which=20
was already covered by a Marginal.=20


New Mexico...=20
Afternoon convection over the Sacramento Mtns brings a threat for=20
runoff issues from burn scars into this evening, so the Marginal=20
Risk is maintained.


Jackson


Day 2
Valid 12Z Sun May 04 2025 - 12Z Mon May 05 2025

...THERE IS A MARGINAL RISK OF EXCESSIVE RAINFALL OVER PARTS OF THE
EASTERN UNITED STATES AND SOUTHERN ROCKIES AND ADJACENT HIGH PLAINS...

The risk of excessive rainfall persists across parts of the Mid-
Atlantic and Southeast US as a slow moving closed low embedded
within a broader upper trough continues to make its way eastward. Deepest moisture of 1.25 to 1.5 inches will be eventually be shunted off-
shore late in the period. Until then...isolated downpours are
possible with spaghetti plots of 2 and 3-inches of rain in 24 hours
mainly being produced by models with the ARW core...but enough
members from the NMM core and from the GEFS to warrant a Marginal.
The western boundary of the Marginal was trimmed compared with the
previous outlook given the models being more progressive with the
surface cold front and the push of drier air being brought in
behind the front.

There is also a Marginal Risk area over parts of New Mexico again
as moisture continue to spread northward and westward from the
Gulf. After 00Z...the flow aloft between the westerly subtropical
jet and a jet streak and low- and mid-levels become increasingly
diffluent with height falls beginning ahead of an approaching
closed low from the west. This...along with moisture and a low
level boundary already in place...should support late day and
evening storms that may produce locally heavy rainfall rates.


Bann

Day 3
Valid 12Z Mon May 05 2025 - 12Z Tue May 06 2025

...THERE IS A SLIGHT RISK OF EXCESSIVE RAINFALL OVER PORTIONS OF
THE HIGH PLAINS ADJACENT TO THE SOUTHERN ROCKIES...

Shortwave energy rotating around the periphery of an upper low
making its way over the Southwest US will trigger late day
thunderstorms on Monday over parts of West Texas that grow upscale
in terms of both coverage and rainfall amounts through much of
Monday night/early Tuesday morning. A feed of low level moisture
being forced upslope ahead of the approaching shortwave will help
fuel the potential for downpours and locally heavy rainfall amounts
leading to the potential of flash flooding. QPF from the
operational models have maximum amounts of rainfall in the 2.5 to
3.8 inches...which tended to be supported by the SREF and GEFS
spaghetti plots and by machine learning first guess EROs. Felt a
Slight Risk area covers the potential for time being.

Bann


Day 1 threat area: https://urldefense.com/v3/__https://www.wpc.ncep.noaa.go= v/qpf/94epoints.txt__;!!DZ3fjg!4p0s8cSHTpSumRt7ojK4BgBep2S_TTZtjWBnuprwC1FC= p8nEN7RAnMHrVSpT9rD1r1O7Fgb7ruOuDKIIuSyorAdLLsk$=20
Day 2 threat area: https://urldefense.com/v3/__https://www.wpc.ncep.noaa.go= v/qpf/98epoints.txt__;!!DZ3fjg!4p0s8cSHTpSumRt7ojK4BgBep2S_TTZtjWBnuprwC1FC= p8nEN7RAnMHrVSpT9rD1r1O7Fgb7ruOuDKIIuSyom7ZqxxU$=20
Day 3 threat area: https://urldefense.com/v3/__https://www.wpc.ncep.noaa.go= v/qpf/99epoints.txt__;!!DZ3fjg!4p0s8cSHTpSumRt7ojK4BgBep2S_TTZtjWBnuprwC1FC= p8nEN7RAnMHrVSpT9rD1r1O7Fgb7ruOuDKIIuSyoqwom3do$=20

=3D =3D =3D
To unsubscribe from WX-STORM and you already have a login, go to https://lists.illinois.edu and use the "Unsubscribe" link. Otherwise email Chris Novy at cnovy@cox.net and ask to be removed from WX-STORM.

--- SBBSecho 3.20-Linux
* Origin: capitolcityonline.net * Telnet/SSH:2022/HTTP (1:2320/105)

FOUS30 KWBC 031654=20
QPFERD

Excessive Rainfall Discussion
NWS Weather Prediction Center College Park MD
1254 PM EDT Sat May 3 2025

Day 1
Valid 16Z Sat May 03 2025 - 12Z Sun May 04 2025

...THERE IS A MARGINAL RISK OF EXCESSIVE RAINFALL FOR MUCH OF THE
EASTERN U.S. AND THE SACRAMENTO MOUNTAINS OF NEW MEXICO...

16Z Update...
An upper-level low is forming over the mid-Mississippi region and
becomes cutoff over Kentucky tonight as the jet focuses over
eastern Canada. Low level flow is drawing Gulf moisture through and
ahead of the system from the Gulf Coast up through the Eastern
Seaboard. Several focus areas for thunderstorms are expected
through tonight in the broad area which covered by a contiguous
Marginal Risk.

Ohio Valley to Gulf Coast...
Locally heavy activity has developed ahead of a surface low over
western TN with scattered storms south ahead of the advancing cold
front through MS and north along a stalled boundary that extends to
the upper Ohio Valley. This activity may pivot over eastern
KY/southern OH through the middle afternoon while activity over AL
to the Gulf Coast should be more progressive.

Carolinas, Central Appalachians and Mid-Atlantic...
Lee trough development over the Piedmont in the Carolinas later
this afternoon will allow potentially training activity in deep
SSWly flow there well into the evening, so the Marginal Risk was
expanded east a bit over SC/NC. This activity lifts north through
the central Appalachians into this evening with localized flash
flood threats. Later tonight the activity shifts east with some
training potential, so the Marginal was maintained east through the Baltimore/Washington urban centers.


Northeast...
The northern end of the moisture plume converges on a frontal zone
over Upstate NY and central New England through this afternoon
bringing potential for excessive rain despite strong deep layer
flow. The Marginal Risk was expanded north into central New
England. A second round of development is expected farther south
this evening in the Hudson Valley and southern New England which
was already covered by a Marginal.


New Mexico...
Afternoon convection over the Sacramento Mtns brings a threat for
runoff issues from burn scars into this evening, so the Marginal
Risk is maintained.


Jackson

Day 2
Valid 12Z Sun May 04 2025 - 12Z Mon May 05 2025

...THERE IS A MARGINAL RISK OF EXCESSIVE RAINFALL OVER PARTS OF THE
EASTERN UNITED STATES AND SOUTHERN ROCKIES AND ADJACENT HIGH PLAINS...

The risk of excessive rainfall persists across parts of the Mid-
Atlantic and Southeast US as a slow moving closed low embedded
within a broader upper trough continues to make its way eastward. Deepest moisture of 1.25 to 1.5 inches will be eventually be shunted off-
shore late in the period. Until then...isolated downpours are
possible with spaghetti plots of 2 and 3-inches of rain in 24 hours
mainly being produced by models with the ARW core...but enough
members from the NMM core and from the GEFS to warrant a Marginal.
The western boundary of the Marginal was trimmed compared with the
previous outlook given the models being more progressive with the
surface cold front and the push of drier air being brought in
behind the front.

There is also a Marginal Risk area over parts of New Mexico again
as moisture continue to spread northward and westward from the
Gulf. After 00Z...the flow aloft between the westerly subtropical
jet and a jet streak and low- and mid-levels become increasingly
diffluent with height falls beginning ahead of an approaching
closed low from the west. This...along with moisture and a low
level boundary already in place...should support late day and
evening storms that may produce locally heavy rainfall rates.


Bann

Day 3
Valid 12Z Mon May 05 2025 - 12Z Tue May 06 2025

...THERE IS A SLIGHT RISK OF EXCESSIVE RAINFALL OVER PORTIONS OF
THE HIGH PLAINS ADJACENT TO THE SOUTHERN ROCKIES...

Shortwave energy rotating around the periphery of an upper low
making its way over the Southwest US will trigger late day
thunderstorms on Monday over parts of West Texas that grow upscale
in terms of both coverage and rainfall amounts through much of
Monday night/early Tuesday morning. A feed of low level moisture
being forced upslope ahead of the approaching shortwave will help
fuel the potential for downpours and locally heavy rainfall amounts
leading to the potential of flash flooding. QPF from the
operational models have maximum amounts of rainfall in the 2.5 to
3.8 inches...which tended to be supported by the SREF and GEFS
spaghetti plots and by machine learning first guess EROs. Felt a
Slight Risk area covers the potential for time being.

Bann


Day 1 threat area: https://urldefense.com/v3/__https://www.wpc.ncep.noaa.go= v/qpf/94epoints.txt__;!!DZ3fjg!7j46e3m58JyDO_IfGcJlZTvfZblplHDUgzA6Phn4uLy8= qJLnw0DDDQf8bOP8hVAT3-7CgzocNhN3er5yRguCj96qOLI$=20
Day 2 threat area: https://urldefense.com/v3/__https://www.wpc.ncep.noaa.go= v/qpf/98epoints.txt__;!!DZ3fjg!7j46e3m58JyDO_IfGcJlZTvfZblplHDUgzA6Phn4uLy8= qJLnw0DDDQf8bOP8hVAT3-7CgzocNhN3er5yRguCuWHgPL4$=20
Day 3 threat area: https://urldefense.com/v3/__https://www.wpc.ncep.noaa.go= v/qpf/99epoints.txt__;!!DZ3fjg!7j46e3m58JyDO_IfGcJlZTvfZblplHDUgzA6Phn4uLy8= qJLnw0DDDQf8bOP8hVAT3-7CgzocNhN3er5yRguCXUTHdTw$=20

=3D =3D =3D
To unsubscribe from WX-STORM and you already have a login, go to https://lists.illinois.edu and use the "Unsubscribe" link. Otherwise email Chris Novy at cnovy@cox.net and ask to be removed from WX-STORM.

--- SBBSecho 3.20-Linux
* Origin: capitolcityonline.net * Telnet/SSH:2022/HTTP (1:2320/105)

FOUS30 KWBC 032029
QPFERD

Excessive Rainfall Discussion
NWS Weather Prediction Center College Park MD
429 PM EDT Sat May 3 2025

Day 1
Valid 16Z Sat May 03 2025 - 12Z Sun May 04 2025

...THERE IS A MARGINAL RISK OF EXCESSIVE RAINFALL FOR MUCH OF THE
EASTERN U.S. AND THE SACRAMENTO MOUNTAINS OF NEW MEXICO...

16Z Update...
An upper-level low is forming over the mid-Mississippi region and
becomes cutoff over Kentucky tonight as the jet focuses over
eastern Canada. Low level flow is drawing Gulf moisture through and
ahead of the system from the Gulf Coast up through the Eastern
Seaboard. Several focus areas for thunderstorms are expected
through tonight in the broad area which covered by a contiguous
Marginal Risk.

Ohio Valley to Gulf Coast...
Locally heavy activity has developed ahead of a surface low over
western TN with scattered storms south ahead of the advancing cold
front through MS and north along a stalled boundary that extends to
the upper Ohio Valley. This activity may pivot over eastern
KY/southern OH through the middle afternoon while activity over AL
to the Gulf Coast should be more progressive.

Carolinas, Central Appalachians and Mid-Atlantic...
Lee trough development over the Piedmont in the Carolinas later
this afternoon will allow potentially training activity in deep
SSWly flow there well into the evening, so the Marginal Risk was
expanded east a bit over SC/NC. This activity lifts north through
the central Appalachians into this evening with localized flash
flood threats. Later tonight the activity shifts east with some
training potential, so the Marginal was maintained east through the Baltimore/Washington urban centers.


Northeast...
The northern end of the moisture plume converges on a frontal zone
over Upstate NY and central New England through this afternoon
bringing potential for excessive rain despite strong deep layer
flow. The Marginal Risk was expanded north into central New
England. A second round of development is expected farther south
this evening in the Hudson Valley and southern New England which
was already covered by a Marginal.


New Mexico...
Afternoon convection over the Sacramento Mtns brings a threat for
runoff issues from burn scars into this evening, so the Marginal
Risk is maintained.


Jackson

Day 2
Valid 12Z Sun May 04 2025 - 12Z Mon May 05 2025

...THERE IS A SLIGHT RISK OF EXCESSIVE RAINFALL OVER PARTS OF THE=20
EASTERN UNITED STATES AND SOUTHERN ROCKIES AND ADJACENT HIGH=20
PLAINS...

21Z Update...


New Mexico...
A Slight Risk has been raised for portions of eastern NM based on a
notable increase in QPF from the 12Z guidance consensus. SWly flow
over TX brings robust Gulf moisture up through the southern Rockies
and adjacent High Plains as a closed low develops and stalls
over the Sonoran Desert. Heavy rain develops in the diurnal
activity that then persists over the southern High Plains well into
Sunday night as the low stalls. The PW anomaly reaches 2 sigma over
this area by 00Z Monday. The 12Z HREF mean suggests some repeating
threats for 1"/hr rates through this Slight area with potential for
2-3" over much of the area. The Marginal risk was expanded to the=20
lower flanks of the San Juans based on updated QPF and FFG.

Great Basin...
Sunday is the second day for the Great Basin under the upper=20
trough. With PW anomalies of 2-3 sigma over normal with instability
and fairly light deep layer flow should allow some repeating
activity over Nevada and the Mojave Desert where a Marginal Risk is
raised.

Midwest to Northeast...
The slow moving closed low embedded within a broader upper trough=20
continues to make its way eastward Sunday. Deepest moisture of=20
1.25 to 1.5 inches will be eventually be shunted off the Mid-
Atlantic coast Sunday afternoon, but still stream in over NY back
through northern Ohio. The Marginal Risk is maintained with an
expansion over the Detroit metro given 12Z QPF consensus along with
lower FFG.


Jackson

Day 3
Valid 12Z Mon May 05 2025 - 12Z Tue May 06 2025

...THERE IS A SLIGHT RISK OF EXCESSIVE RAINFALL OVER PORTIONS WEST
TEXAS...

Texas into New Mexico...
The upper low drifts east over southern AZ Monday, causing a minor
shift east in downstream rainfall compared to Sunday. Confidence=20
remains in a focused area for repeating heavy rain south from the=20
TX Panhandle to the NM border where a Slight Risk remains (it was=20
expanded a bit west through the NM border). A bit of a lull in QPF=20
is expected Monday morning, but diurnal increases expected in the=20
afternoon that then persist into or through the night. The PW
anomaly is forecast to exceed 2 sigma by 00Z Tuesday with the 1.25"
PW line reaching the Caprock. The 12Z QPF consensus is for 2-4"
over a sizable area just south of the TX Panhandle.


Mojave Desert through Southern Utah...
The broadening upper low over AZ aids instability over the Mojave
Desert through northern AZ and southern/central UT where a Marginal
Risk is raised for Monday. Continued light deep layer flow and PW=20
anomalies of 2-3 sigma should allow slow moving, heavy=20
thunderstorms over this area which includes the Slot Canyons of=20
southern UT.


Northern Mid-Atlantic into southern New England...
Closed low meanders to the Upper OH Valley Monday night. Continued
onshore flow brings the threat for repeating locally heavy rain
over the northern Mid-Atlantic into southern New England which will
have seen some heavy rain between now and then. A Marginal Risk is
maintained.


Jackson


Day 1 threat area: https://urldefense.com/v3/__https://www.wpc.ncep.noaa.go= v/qpf/94epoints.txt__;!!DZ3fjg!83gotFJ6QqLkVIynu_UiLj2u41RMP9nFtFBdgESzokMF= aDwcfJce0OXH9_Hh_3_7KuRIQSQYWIetoOL0FvRqme8E4zM$=20
Day 2 threat area: https://urldefense.com/v3/__https://www.wpc.ncep.noaa.go= v/qpf/98epoints.txt__;!!DZ3fjg!83gotFJ6QqLkVIynu_UiLj2u41RMP9nFtFBdgESzokMF= aDwcfJce0OXH9_Hh_3_7KuRIQSQYWIetoOL0FvRqzf2hGLk$=20
Day 3 threat area: https://urldefense.com/v3/__https://www.wpc.ncep.noaa.go= v/qpf/99epoints.txt__;!!DZ3fjg!83gotFJ6QqLkVIynu_UiLj2u41RMP9nFtFBdgESzokMF= aDwcfJce0OXH9_Hh_3_7KuRIQSQYWIetoOL0FvRqc2uWAzY$=20

=3D =3D =3D
To unsubscribe from WX-STORM and you already have a login, go to https://lists.illinois.edu and use the "Unsubscribe" link. Otherwise email Chris Novy at cnovy@cox.net and ask to be removed from WX-STORM.

--- SBBSecho 3.20-Linux
* Origin: capitolcityonline.net * Telnet/SSH:2022/HTTP (1:2320/105)

FOUS30 KWBC 032037
QPFERD

Excessive Rainfall Discussion
NWS Weather Prediction Center College Park MD
437 PM EDT Sat May 3 2025

Day 1
Valid 16Z Sat May 03 2025 - 12Z Sun May 04 2025

...THERE IS A MARGINAL RISK OF EXCESSIVE RAINFALL FOR MUCH OF THE
EASTERN U.S. AND THE SACRAMENTO MOUNTAINS OF NEW MEXICO...

16Z Update...
An upper-level low is forming over the mid-Mississippi region and
becomes cutoff over Kentucky tonight as the jet focuses over
eastern Canada. Low level flow is drawing Gulf moisture through and
ahead of the system from the Gulf Coast up through the Eastern
Seaboard. Several focus areas for thunderstorms are expected
through tonight in the broad area which covered by a contiguous
Marginal Risk.

Ohio Valley to Gulf Coast...
Locally heavy activity has developed ahead of a surface low over
western TN with scattered storms south ahead of the advancing cold
front through MS and north along a stalled boundary that extends to
the upper Ohio Valley. This activity may pivot over eastern
KY/southern OH through the middle afternoon while activity over AL
to the Gulf Coast should be more progressive.

Carolinas, Central Appalachians and Mid-Atlantic...
Lee trough development over the Piedmont in the Carolinas later
this afternoon will allow potentially training activity in deep
SSWly flow there well into the evening, so the Marginal Risk was
expanded east a bit over SC/NC. This activity lifts north through
the central Appalachians into this evening with localized flash
flood threats. Later tonight the activity shifts east with some
training potential, so the Marginal was maintained east through the Baltimore/Washington urban centers.


Northeast...
The northern end of the moisture plume converges on a frontal zone
over Upstate NY and central New England through this afternoon
bringing potential for excessive rain despite strong deep layer
flow. The Marginal Risk was expanded north into central New
England. A second round of development is expected farther south
this evening in the Hudson Valley and southern New England which
was already covered by a Marginal.


New Mexico...
Afternoon convection over the Sacramento Mtns brings a threat for
runoff issues from burn scars into this evening, so the Marginal
Risk is maintained.


Jackson

Day 2
Valid 12Z Sun May 04 2025 - 12Z Mon May 05 2025

...THERE IS A SLIGHT RISK OF EXCESSIVE RAINFALL OVER PARTS OF THE
EASTERN UNITED STATES AND SOUTHERN ROCKIES AND ADJACENT HIGH
PLAINS...

21Z Update...


New Mexico...
A Slight Risk has been raised for portions of eastern NM based on a
notable increase in QPF from the 12Z guidance consensus. SWly flow
over TX brings robust Gulf moisture up through the southern Rockies
and adjacent High Plains as a closed low develops and stalls
over the Sonoran Desert. Heavy rain develops in the diurnal
activity that then persists over the southern High Plains well into
Sunday night as the low stalls. The PW anomaly reaches 2 sigma over
this area by 00Z Monday. The 12Z HREF mean suggests some repeating
threats for 1"/hr rates through this Slight area with potential for
2-3" over much of the area. The Marginal risk was expanded to the
lower flanks of the San Juans based on updated QPF and FFG.

Great Basin...
Sunday is the second day for the Great Basin under the upper
trough. With PW anomalies of 2-3 sigma over normal with instability
and fairly light deep layer flow should allow some repeating
activity over Nevada and the Mojave Desert where a Marginal Risk is
raised.

Midwest to Northeast...
The slow moving closed low embedded within a broader upper trough
continues to make its way eastward Sunday. Deepest moisture of
1.25 to 1.5 inches will be eventually be shunted off the Mid-
Atlantic coast Sunday afternoon, but still stream in over NY back
through northern Ohio. The Marginal Risk is maintained with an
expansion over the Detroit metro given 12Z QPF consensus along with
lower FFG.


Jackson

Day 3
Valid 12Z Mon May 05 2025 - 12Z Tue May 06 2025

...THERE IS A SLIGHT RISK OF EXCESSIVE RAINFALL OVER PORTIONS OF WEST
TEXAS...

Texas into New Mexico...
The upper low drifts east over southern AZ Monday, causing a minor
shift east in downstream rainfall compared to Sunday. Confidence
remains in a focused area for repeating heavy rain south from the
TX Panhandle to the NM border where a Slight Risk remains (it was
expanded a bit west through the NM border). A bit of a lull in QPF
is expected Monday morning, but diurnal increases expected in the
afternoon that then persist into or through the night. The PW
anomaly is forecast to exceed 2 sigma by 00Z Tuesday with the 1.25"
PW line reaching the Caprock. The 12Z QPF consensus is for 2-4"
over a sizable area just south of the TX Panhandle.


Mojave Desert through Southern Utah...
The broadening upper low over AZ aids instability over the Mojave
Desert through northern AZ and southern/central UT where a Marginal
Risk is raised for Monday. Continued light deep layer flow and PW
anomalies of 2-3 sigma should allow slow moving, heavy
thunderstorms over this area which includes the Slot Canyons of
southern UT.


Northern Mid-Atlantic into southern New England...
Closed low meanders to the Upper OH Valley Monday night. Continued
onshore flow brings the threat for repeating locally heavy rain
over the northern Mid-Atlantic into southern New England which will
have seen some heavy rain between now and then. A Marginal Risk is
maintained.


Jackson


Day 1 threat area: https://urldefense.com/v3/__https://www.wpc.ncep.noaa.go= v/qpf/94epoints.txt__;!!DZ3fjg!_5_IjFrWArYNhKbX3d93uvm_ogG1W_rlPbutYb2tCOlu= bLJ34v2McXYld19HY3hd9DHe8vfDxoLlDJDqxymVInWs2FU$=20
Day 2 threat area: https://urldefense.com/v3/__https://www.wpc.ncep.noaa.go= v/qpf/98epoints.txt__;!!DZ3fjg!_5_IjFrWArYNhKbX3d93uvm_ogG1W_rlPbutYb2tCOlu= bLJ34v2McXYld19HY3hd9DHe8vfDxoLlDJDqxymVEdCWK2M$=20
Day 3 threat area: https://urldefense.com/v3/__https://www.wpc.ncep.noaa.go= v/qpf/99epoints.txt__;!!DZ3fjg!_5_IjFrWArYNhKbX3d93uvm_ogG1W_rlPbutYb2tCOlu= bLJ34v2McXYld19HY3hd9DHe8vfDxoLlDJDqxymV3TXyul0$=20

=3D =3D =3D
To unsubscribe from WX-STORM and you already have a login, go to https://lists.illinois.edu and use the "Unsubscribe" link. Otherwise email Chris Novy at cnovy@cox.net and ask to be removed from WX-STORM.

--- SBBSecho 3.20-Linux
* Origin: capitolcityonline.net * Telnet/SSH:2022/HTTP (1:2320/105)

FOUS30 KWBC 040048
QPFERD

Excessive Rainfall Discussion
NWS Weather Prediction Center College Park MD
848 PM EDT Sat May 3 2025

Day 1
Valid 01Z Sun May 04 2025 - 12Z Sun May 04 2025

...THERE IS A MARGINAL RISK OF EXCESSIVE RAINFALL FOR PORTIONS OF=20
THE EASTERN U.S. ...

...01Z Update...

The Marginal Risk area for the Sacramento Mountains of New Mexico
was removed as the shower activity over the area wanes with sunset
approaching.

The Marginal for the eastern U.S. was trimmed from the west behind
the eastward moving convection over the Southeast, as well as from
the lower Ohio Valley, where the rain in Indiana, Illinois, and
Missouri has been mostly stratiform all day and hasn't posed a
flash flooding threat.

The Marginal in the Northeast was expanded eastward to include
Philadelphia, NYC, Long Island, and Boston. Potent convection
moving northeast in these areas may pose a localized flash flooding
threat in any of those urban centers. It as also expanded a couple
rows of counties east in the Carolinas ahead of the slow moving
line of storms there. Those storms should wane with nightfall as
they move into eastern North Carolina.=20

Wegman

Day 2
Valid 12Z Sun May 04 2025 - 12Z Mon May 05 2025

...THERE IS A SLIGHT RISK OF EXCESSIVE RAINFALL OVER PARTS OF THE
EASTERN UNITED STATES AND SOUTHERN ROCKIES AND ADJACENT HIGH
PLAINS...

21Z Update...


New Mexico...
A Slight Risk has been raised for portions of eastern NM based on a
notable increase in QPF from the 12Z guidance consensus. SWly flow
over TX brings robust Gulf moisture up through the southern Rockies
and adjacent High Plains as a closed low develops and stalls
over the Sonoran Desert. Heavy rain develops in the diurnal
activity that then persists over the southern High Plains well into
Sunday night as the low stalls. The PW anomaly reaches 2 sigma over
this area by 00Z Monday. The 12Z HREF mean suggests some repeating
threats for 1"/hr rates through this Slight area with potential for
2-3" over much of the area. The Marginal risk was expanded to the
lower flanks of the San Juans based on updated QPF and FFG.

Great Basin...
Sunday is the second day for the Great Basin under the upper
trough. With PW anomalies of 2-3 sigma over normal with instability
and fairly light deep layer flow should allow some repeating
activity over Nevada and the Mojave Desert where a Marginal Risk is
raised.

Midwest to Northeast...
The slow moving closed low embedded within a broader upper trough
continues to make its way eastward Sunday. Deepest moisture of
1.25 to 1.5 inches will be eventually be shunted off the Mid-
Atlantic coast Sunday afternoon, but still stream in over NY back
through northern Ohio. The Marginal Risk is maintained with an
expansion over the Detroit metro given 12Z QPF consensus along with
lower FFG.


Jackson

Day 3
Valid 12Z Mon May 05 2025 - 12Z Tue May 06 2025

...THERE IS A SLIGHT RISK OF EXCESSIVE RAINFALL OVER PORTIONS OF WEST
TEXAS...

Texas into New Mexico...
The upper low drifts east over southern AZ Monday, causing a minor
shift east in downstream rainfall compared to Sunday. Confidence
remains in a focused area for repeating heavy rain south from the
TX Panhandle to the NM border where a Slight Risk remains (it was
expanded a bit west through the NM border). A bit of a lull in QPF
is expected Monday morning, but diurnal increases expected in the
afternoon that then persist into or through the night. The PW
anomaly is forecast to exceed 2 sigma by 00Z Tuesday with the 1.25"
PW line reaching the Caprock. The 12Z QPF consensus is for 2-4"
over a sizable area just south of the TX Panhandle.


Mojave Desert through Southern Utah...
The broadening upper low over AZ aids instability over the Mojave
Desert through northern AZ and southern/central UT where a Marginal
Risk is raised for Monday. Continued light deep layer flow and PW
anomalies of 2-3 sigma should allow slow moving, heavy
thunderstorms over this area which includes the Slot Canyons of
southern UT.


Northern Mid-Atlantic into southern New England...
Closed low meanders to the Upper OH Valley Monday night. Continued
onshore flow brings the threat for repeating locally heavy rain
over the northern Mid-Atlantic into southern New England which will
have seen some heavy rain between now and then. A Marginal Risk is
maintained.


Jackson


Day 1 threat area: https://urldefense.com/v3/__https://www.wpc.ncep.noaa.go= v/qpf/94epoints.txt__;!!DZ3fjg!6WKrsfExSs7Do3eTFPK8wplQVm5kZE2Z9UkjvrtXGjHj= DWwBKuhrkUor-FKJiRnVM_estwK5Iwkd1Y8WNJnVVE8X0vY$=20
Day 2 threat area: https://urldefense.com/v3/__https://www.wpc.ncep.noaa.go= v/qpf/98epoints.txt__;!!DZ3fjg!6WKrsfExSs7Do3eTFPK8wplQVm5kZE2Z9UkjvrtXGjHj= DWwBKuhrkUor-FKJiRnVM_estwK5Iwkd1Y8WNJnV_oHr87Y$=20
Day 3 threat area: https://urldefense.com/v3/__https://www.wpc.ncep.noaa.go= v/qpf/99epoints.txt__;!!DZ3fjg!6WKrsfExSs7Do3eTFPK8wplQVm5kZE2Z9UkjvrtXGjHj= DWwBKuhrkUor-FKJiRnVM_estwK5Iwkd1Y8WNJnV_kvDza8$=20

=3D =3D =3D
To unsubscribe from WX-STORM and you already have a login, go to https://lists.illinois.edu and use the "Unsubscribe" link. Otherwise email Chris Novy at cnovy@cox.net and ask to be removed from WX-STORM.

--- SBBSecho 3.20-Linux
* Origin: capitolcityonline.net * Telnet/SSH:2022/HTTP (1:2320/105)

FOUS30 KWBC 040831
QPFERD

Excessive Rainfall Discussion
NWS Weather Prediction Center College Park MD
431 AM EDT Sun May 4 2025

Day 1
Valid 12Z Sun May 04 2025 - 12Z Mon May 05 2025

...THERE IS A SLIGHT RISK OF EXCESSIVE RAINFALL OVER PORTIONS OF
THE HIGH PLAINS ADJACENT TO THE SOUTHERN ROCKIES...

New Mexico...
There is a slight risk of excessive rainfall over portions of
eastern New Mexico as south to southeasterly flow draws moisture
into the region as height falls begin in response to shortwave
energy approaches. The 04/00Z suite of numerical guidance develops
heavy rainfall developing in the diurnal activity that then=20
persists over the southern High Plains well into late tonight/early
Monday morning. Precipitable water anomaly values reaches 2 sigma=20
over this area by 00Z Monday..with the 04/00Z HREF mean suggests=20
some repeating threats for 1"/hr rates across the Slight area with=20
potential for 2-3" over much of the area. The eastern portion of=20
the Marginal risk area was largely left unchanged...but the western
portion of the area was trimmed to minimize overlap with heavy=20
snow areas (especially over the San Juan mountains).

Great Basin...
While the probability of excessive rainfall is likely non-zero
given the showery nature of precipitation given the upper trough=20
and cold mid- level temperatures aloft...the amount of rain=20
shouldn't be a problem unless it all falls in under an hour.
Individual thunderstorms may result in briefly heavy
rates...but thinking is that the thunderstorms will be embedded=20
within a broader field of showers circulating around the main upper
low. This should help mitigate the overall threat of flooding.

Midwest to Northeast...
The slow moving closed low embedded within a broader upper trough
continues to make its way eastward across the Ohio Valley today and
tonight. Deepest moisture of 1.25 to 1.5 inches will be eventually
be shunted off the Mid- Atlantic coast today but still stream in=20
over New York back and then drawn back through northern Ohio. The=20
Marginal Risk is maintained with only nudges to the
western/northern periphery of the Marginal risk area based on the
latest QPF.=20

Bann

Day 2
Valid 12Z Mon May 05 2025 - 12Z Tue May 06 2025

...THERE IS A SLIGHT RISK OF EXCESSIVE RAINFALL OVER PORTIONS OF
THE SOUTHERN HIGH PLAINS...

Texas into New Mexico...
A closed upper low over the Desert Southwest will continue to
meander eastward on Monday. Confidence remains in a focused area=20
for repeating heavy rainfall south from the TX Panhandle to the NM
border where a Slight Risk remains without many changes...with main
activity occurring once again around the time of maximum daytime
heating and then persisting into or through the night. The suite=20
of 04/00Z numerical guidance still shows the magnitude of=20
precipitable water values to exceed 2 sigma by 00Z Tuesday with the
1.25" precipitable water line reaching the Caprock. The 12Z QPF=20
consensus is for 2-4" over a sizable area just south of the TX=20 Panhandle...with locally higher amounts embedded in the broader QPF
area.

Mojave Desert through Southern Utah...
Numerous showers with embedded daytime and evening thunderstorms is
still expected as upper low continues to meander over Arizona as=20
it begins to fill. Moisture is still anomalous for this time of=20
year...being some 2 to 3 standardized anomalies above climatology=20
for early May...but concern would be greater for excessive rainfall
if the actual values of precipitable water values were greater and
intense rainfall rates would be sustained for a longer duration.=20
As a result...the risk of excessive rainfall appears to be non-zero
but not enough to warrant a Marginal risk area based on=20
coordination with local offices.

Northern Mid-Atlantic into southern New England...
Closed low will continue to meanders across portions of the Upper=20
OH Valley through Monday night. Continued onshore flow brings the=20
threat for repeating locally heavy rain over the northern Mid-=20
Atlantic into southern New England which will have seen some heavy=20
rain between now and then. A Marginal Risk is maintained.


Bann

Day 3
Valid 12Z Tue May 06 2025 - 12Z Wed May 07 2025

...THERE IS A MODERATE RISK OF EXCESSIVE RAINFALL OVER PORTIONS OF
THE SOUTHERN MISSISSIPPI VALLEY/CENTRAL GULF COAST REGION...

Showers and thunderstorms capable of producing intense rainfall
rates and heavy/excessive rainfall will become more numerous=20=20
on Tuesday as height falls make their way out across Texas and as
the parent upper low ejects out over the Southern Plains. With
increasing flow off the Gulf drawing deeper moisture on-
shore....the convection should become increasingly efficient=20
rainfall makers.especially over portions of Louisiana and=20
Mississippi. There is still some differences in where models place=20
the heaviest rainfall...with the GFS and Canadian favoring a faster
solution while the EC/UK favoring the axis from eastern Texas into
northern Louisiana. This forecast cycle nudged the Moderate risk=20
area a bit eastward but not as far east as the GFS/Canadian.

Bann


Day 1 threat area: https://urldefense.com/v3/__https://www.wpc.ncep.noaa.go= v/qpf/94epoints.txt__;!!DZ3fjg!6dTVjEEkBIyndyMa9Gh5Zi_Ce7BxVBqHlgPlVou7vCQS= Y9Ykfz-I1t8Lkkkl0R4tBCGHFHdwFp-6sNEj9-aOP5VZSDA$=20
Day 2 threat area: https://urldefense.com/v3/__https://www.wpc.ncep.noaa.go= v/qpf/98epoints.txt__;!!DZ3fjg!6dTVjEEkBIyndyMa9Gh5Zi_Ce7BxVBqHlgPlVou7vCQS= Y9Ykfz-I1t8Lkkkl0R4tBCGHFHdwFp-6sNEj9-aOjeHnvSo$=20
Day 3 threat area: https://urldefense.com/v3/__https://www.wpc.ncep.noaa.go= v/qpf/99epoints.txt__;!!DZ3fjg!6dTVjEEkBIyndyMa9Gh5Zi_Ce7BxVBqHlgPlVou7vCQS= Y9Ykfz-I1t8Lkkkl0R4tBCGHFHdwFp-6sNEj9-aOX1u4wL8$=20

=3D =3D =3D
To unsubscribe from WX-STORM and you already have a login, go to https://lists.illinois.edu and use the "Unsubscribe" link. Otherwise email Chris Novy at cnovy@cox.net and ask to be removed from WX-STORM.

--- SBBSecho 3.20-Linux
* Origin: capitolcityonline.net * Telnet/SSH:2022/HTTP (1:2320/105)

FOUS30 KWBC 041552
QPFERD

Excessive Rainfall Discussion
NWS Weather Prediction Center College Park MD
1152 AM EDT Sun May 4 2025

Day 1
Valid 16Z Sun May 04 2025 - 12Z Mon May 05 2025

...THERE IS A SLIGHT RISK OF EXCESSIVE RAINFALL FOR PORTIONS OF
EASTERN NEW MEXICO...

...16Z Update...

...New Mexico...

The Slight Risk area across New Mexico was expanded slightly south
in keeping with the latest guidance that areas north of Roswell
could see more rainfall than previous forecasts, necessitating the
southward expansion. Otherwise, the forecast is little changed in
this area with a broad 1-2 inches of rain expected, most of which
occurring tonight. Flooding concerns stemming from the slow
movement of the storms, a consistent resupply of Gulf moisture from
the southeast on 20-30 kt southeasterly winds, and nearly
stationary forcing in the form of a cutoff low all support widely
scattered instance of flash flooding consistent with the Slight
Risk. Areas of terrain will be especially vulnerable due to the
terrain focusing the rainfall into narrow valleys that can fill up
and flooding with relatively little rainfall.

...Northeast...

As the cold frontal rainfall moves off the coast over the next few
hours, the Marginal Risk in NC,VA, and MD was trimmed from the
south and west to follow the line of showers with embedded
convection as it moves over the beaches of those states. Isolated
afternoon thunderstorms will be possible given the abundance of
moisture from today's rains across the Piedmont of NC and VA, but
the storms should be few and far between, and therefore not pose a
significant flash flooding threat. From about the Mason-Dixon line
north this afternoon, increasing instability should allow for more
widely scattered convection, as compared to areas further south.
THese storms will be capable of producing isolated instances of=20
flash flooding.

The Marginal was also trimmed out of MI, IN, and western OH since=20
the rainfall there is expected to remain the stratiform it is now,=20
which would preclude any rainfall rates capable of causing flash=20
flooding. Elsewhere the Marginal remains in place and largely
unchanged.

Wegman

...Previous Discussion...

New Mexico...
There is a slight risk of excessive rainfall over portions of
eastern New Mexico as south to southeasterly flow draws moisture
into the region as height falls begin in response to shortwave
energy approaches. The 04/00Z suite of numerical guidance develops
heavy rainfall developing in the diurnal activity that then
persists over the southern High Plains well into late tonight/early
Monday morning. Precipitable water anomaly values reaches 2 sigma
over this area by 00Z Monday..with the 04/00Z HREF mean suggests
some repeating threats for 1"/hr rates across the Slight area with
potential for 2-3" over much of the area. The eastern portion of
the Marginal risk area was largely left unchanged...but the western
portion of the area was trimmed to minimize overlap with heavy
snow areas (especially over the San Juan mountains).

Great Basin...
While the probability of excessive rainfall is likely non-zero
given the showery nature of precipitation given the upper trough
and cold mid- level temperatures aloft...the amount of rain
shouldn't be a problem unless it all falls in under an hour.
Individual thunderstorms may result in briefly heavy
rates...but thinking is that the thunderstorms will be embedded
within a broader field of showers circulating around the main upper
low. This should help mitigate the overall threat of flooding.

Midwest to Northeast...
The slow moving closed low embedded within a broader upper trough
continues to make its way eastward across the Ohio Valley today and
tonight. Deepest moisture of 1.25 to 1.5 inches will be eventually
be shunted off the Mid- Atlantic coast today but still stream in
over New York back and then drawn back through northern Ohio. The
Marginal Risk is maintained with only nudges to the
western/northern periphery of the Marginal risk area based on the
latest QPF.

Bann

Day 2
Valid 12Z Mon May 05 2025 - 12Z Tue May 06 2025

...THERE IS A SLIGHT RISK OF EXCESSIVE RAINFALL OVER PORTIONS OF
THE SOUTHERN HIGH PLAINS...

Texas into New Mexico...
A closed upper low over the Desert Southwest will continue to
meander eastward on Monday. Confidence remains in a focused area
for repeating heavy rainfall south from the TX Panhandle to the NM
border where a Slight Risk remains without many changes...with main
activity occurring once again around the time of maximum daytime
heating and then persisting into or through the night. The suite
of 04/00Z numerical guidance still shows the magnitude of
precipitable water values to exceed 2 sigma by 00Z Tuesday with the
1.25" precipitable water line reaching the Caprock. The 12Z QPF
consensus is for 2-4" over a sizable area just south of the TX
Panhandle...with locally higher amounts embedded in the broader QPF
area.

Mojave Desert through Southern Utah...
Numerous showers with embedded daytime and evening thunderstorms is
still expected as upper low continues to meander over Arizona as
it begins to fill. Moisture is still anomalous for this time of
year...being some 2 to 3 standardized anomalies above climatology
for early May...but concern would be greater for excessive rainfall
if the actual values of precipitable water values were greater and
intense rainfall rates would be sustained for a longer duration.
As a result...the risk of excessive rainfall appears to be non-zero
but not enough to warrant a Marginal risk area based on
coordination with local offices.

Northern Mid-Atlantic into southern New England...
Closed low will continue to meanders across portions of the Upper
OH Valley through Monday night. Continued onshore flow brings the
threat for repeating locally heavy rain over the northern Mid-
Atlantic into southern New England which will have seen some heavy
rain between now and then. A Marginal Risk is maintained.


Bann

Day 3
Valid 12Z Tue May 06 2025 - 12Z Wed May 07 2025

...THERE IS A MODERATE RISK OF EXCESSIVE RAINFALL OVER PORTIONS OF
THE SOUTHERN MISSISSIPPI VALLEY/CENTRAL GULF COAST REGION...

Showers and thunderstorms capable of producing intense rainfall
rates and heavy/excessive rainfall will become more numerous
on Tuesday as height falls make their way out across Texas and as
the parent upper low ejects out over the Southern Plains. With
increasing flow off the Gulf drawing deeper moisture on-
shore....the convection should become increasingly efficient
rainfall makers.especially over portions of Louisiana and
Mississippi. There is still some differences in where models place
the heaviest rainfall...with the GFS and Canadian favoring a faster
solution while the EC/UK favoring the axis from eastern Texas into
northern Louisiana. This forecast cycle nudged the Moderate risk
area a bit eastward but not as far east as the GFS/Canadian.

Bann


Day 1 threat area: https://urldefense.com/v3/__https://www.wpc.ncep.noaa.go= v/qpf/94epoints.txt__;!!DZ3fjg!6jJqAaEN23e-9vRyMh25ExJDXVrsEvAZj8EIo1FJJ9C0= hlLHIFyi5FggjqPUzm-vH4h-jAqUNhZkyhOi2C_yPf9WDeI$=20
Day 2 threat area: https://urldefense.com/v3/__https://www.wpc.ncep.noaa.go= v/qpf/98epoints.txt__;!!DZ3fjg!6jJqAaEN23e-9vRyMh25ExJDXVrsEvAZj8EIo1FJJ9C0= hlLHIFyi5FggjqPUzm-vH4h-jAqUNhZkyhOi2C_yQrs2kUc$=20
Day 3 threat area: https://urldefense.com/v3/__https://www.wpc.ncep.noaa.go= v/qpf/99epoints.txt__;!!DZ3fjg!6jJqAaEN23e-9vRyMh25ExJDXVrsEvAZj8EIo1FJJ9C0= hlLHIFyi5FggjqPUzm-vH4h-jAqUNhZkyhOi2C_yrJbbAfs$=20

=3D =3D =3D
To unsubscribe from WX-STORM and you already have a login, go to https://lists.illinois.edu and use the "Unsubscribe" link. Otherwise email Chris Novy at cnovy@cox.net and ask to be removed from WX-STORM.

--- SBBSecho 3.20-Linux
* Origin: capitolcityonline.net * Telnet/SSH:2022/HTTP (1:2320/105)

FOUS30 KWBC 042004
QPFERD

Excessive Rainfall Discussion
NWS Weather Prediction Center College Park MD
404 PM EDT Sun May 4 2025

Day 1
Valid 20Z Sun May 04 2025 - 12Z Mon May 05 2025

...THERE IS A SLIGHT RISK OF EXCESSIVE RAINFALL FOR PORTIONS OF
EASTERN NEW MEXICO...

...20Z Special Update...

Marginal Risk areas have been added to portions of the Southwest as
well as for southern Florida. See MPDs 218 at wpc.ncep.noaa.gov/metwatch/metwatch_mpd_multi.php?md=3D0218&yr=3D2025
for the Southwest and MPD 219 at wpc.ncep.noaa.gov/metwatch/metwatch_mpd_multi.php?md=3D0219&yr=3D2025
for south Florida for more details.

Day 2
Valid 12Z Mon May 05 2025 - 12Z Tue May 06 2025

...THERE IS A SLIGHT RISK OF EXCESSIVE RAINFALL OVER PORTIONS OF
THE SOUTHERN HIGH PLAINS...

...2030Z Update...

...Southern High Plains...

The Slight Risk area was expanded northwestward to include more of
the Texas Panhandle and far eastern New Mexico with this update and
in coordination with ABQ/Albuquerque, NM and AMA/Amarillo, TX
forecast offices. Showers and thunderstorms from the overnight
period will likely be ongoing along the NM/TX border at the start
of the period Monday morning, with periodic flareups of additional
convection expected throughout the day in this same area. Following
occasional daytime convection, a new MCS is likely to form during
the evening across west Texas and eastern NM and track northward
through the night. Thus, portions of the area, likely centered
around Lubbock/southern Texas Panhandle, will likely see multiple
rounds of heavy rain through Monday night. Soils in this area are
well above normal for moisture, especially for the eastern
Panhandle closer to Oklahoma. Therefore lesser amounts of rain than
normal will be needed to result in flash flooding.=20=20

...Northeast...

The Marginal Risk across portions of the Northeast was maintained
with few changes with this update. With coordination from
OKX/Upton, NY; ALY/Albany, NY; BOX/Taunton, MA; and PHI/Mt. Holly,
NJ forecast offices, a Slight Risk upgrade was considered for
portions of the area, with numerous models forecasting a swath of
1-2 inches of rain from NYC north and east through Long Island,
much of Connecticut, and the lower Hudson Valley and Catskills.
Despite that, very nominal instability and dry antecedent soils
conditions and low river levels were determined to likely prevent
much flash flooding outside of the most flood prone areas, so the
Marginal was maintained. Upslope will be a contributing factor to
locally heavier and steadier rain across Connecticut and the lower
Hudson Valley into the Catskills, but here too flash flooding
should be confined to only isolated areas. Should instability
increase or total rainfall increase a targeted Slight Risk may
still be needed with future updates.

Wegman

...Previous Discussion...

Texas into New Mexico...
A closed upper low over the Desert Southwest will continue to
meander eastward on Monday. Confidence remains in a focused area
for repeating heavy rainfall south from the TX Panhandle to the NM
border where a Slight Risk remains without many changes...with main
activity occurring once again around the time of maximum daytime
heating and then persisting into or through the night. The suite
of 04/00Z numerical guidance still shows the magnitude of
precipitable water values to exceed 2 sigma by 00Z Tuesday with the
1.25" precipitable water line reaching the Caprock. The 12Z QPF
consensus is for 2-4" over a sizable area just south of the TX
Panhandle...with locally higher amounts embedded in the broader QPF
area.

Mojave Desert through Southern Utah...
Numerous showers with embedded daytime and evening thunderstorms is
still expected as upper low continues to meander over Arizona as
it begins to fill. Moisture is still anomalous for this time of
year...being some 2 to 3 standardized anomalies above climatology
for early May...but concern would be greater for excessive rainfall
if the actual values of precipitable water values were greater and
intense rainfall rates would be sustained for a longer duration.
As a result...the risk of excessive rainfall appears to be non-zero
but not enough to warrant a Marginal risk area based on
coordination with local offices.

Northern Mid-Atlantic into southern New England...
Closed low will continue to meanders across portions of the Upper
OH Valley through Monday night. Continued onshore flow brings the
threat for repeating locally heavy rain over the northern Mid-
Atlantic into southern New England which will have seen some heavy
rain between now and then. A Marginal Risk is maintained.


Bann

Day 3
Valid 12Z Tue May 06 2025 - 12Z Wed May 07 2025

...THERE IS A MODERATE RISK OF EXCESSIVE RAINFALL OVER PORTIONS OF
THE SOUTHERN MISSISSIPPI VALLEY/CENTRAL GULF COAST REGION...

...2030Z Update...

...Lower Mississippi Valley to the Colorado Front Range...

The inherited Moderate Risk area was greatly expanded with this
update, in keeping with numerous pieces of guidance, ensembles, and
means all favoring a significant thunderstorm training and heavy
rain event across the Arklatex and into central Mississippi. The
RRFS suggests multiple lines of storms will cross west to east
across the Moderate Risk area, starting in the north from northeast
Texas, along the Louisiana/Arkansas border, and then continuing
into Mississippi. The trailing (southwestern) portion of the line
will hang back as it is joined by additional storms over southeast
Texas that progress eastward.

The first line will start out at roughly a southwest to northeast
orientation, however, into Tuesday night, the lines will get
progressively more west-east oriented, meaning greater chance that
repeating lines of storms will move across Louisiana. Meanwhile the
outflow on the northern side of the complex of storms will allow
for continued lighter rains in northern areas that were hard hit
earlier in the evening, which will continue or worsen ongoing flash
flooding as a result of the earlier storms. While the RRFS is far
from a perfect solution as to who will get heavy rain and when,
given the footprint of heavy rain in the RRFS is at least similar
and in a roughly the same location as the heavy rain footprint in
the global models, it appeared to offer a good first guess as to
how the storm evolution will play out through the period.

The Moderate Risk area remains a lower-end Moderate for now until
there is better consensus (and likely southward shifts) in the area
of heaviest rainfall. By then it's possible portions of the area
may be considered in a higher-end Moderate Risk. For now...rainfall
amounts in this area should not reach High Risk levels, since there
is at least some southward movement for most of the storms with
time, so no one area sees heavy rains for an extended duration.
Further, it's possible that the training storms end up offshore of
the Louisiana coast should there be more dramatic southward shifts,
so the Moderate Risk was determined to be the appropriate risk
level for flash flooding. Should there be significant increases
with future runs, that are expected to be more concentrated, then
it's not completely out of the question that a targeted High Risk
may be needed with future updates.

While the heaviest rains will be associated with the moderate Risk
area in portions of the lower Mississippi Valley, a good amount of
that moisture and instability will be drawn northwestward ahead of
a strong shortwave trough associated with the slow-moving upper
level low over the 4 Corners region. This will extend an area of
heavy rain from the MCS/Moderate Risk region northwest across much
of Oklahoma and into southern Colorado. This in turn will lead to a
shearing front, but the heavy rainfall will be moving over areas
hard hit with prior flooding rains, particularly over Oklahoma and
the Panhandles. Thus, the Slight Risk extends well west into
southeastern Colorado, where upslope may play a role in producing
locally heavy rains along the Front Range, while the higher
elevations pick up heavy snow.

...Northeast...

A slow moving upper level low over the Midwest will continue to
pump Atlantic moisture into New England on Tuesday...a continuation
of periods of rain from the same system both today and on Monday.
By Tuesday, however, instability into and south of New England=20
will increase to up to 500 J/kg. While this amount of instability
is far from impressive, it will still be enough to allow for
convective showers and maybe some embedded thunderstorms to move
north up the coast and into New England. Antecedent soil moisture
conditions are likely to be significantly more favorable for the
development of flash flooding in this region considering the rain
expected there today through Monday. Thus, a Slight Risk upgrade is
possible in this area assuming there are increases in the forecast
rainfall once this period moves into the short-term and the CAMs
can analyze the system.

Wegman

...Previous Discussion...

Showers and thunderstorms capable of producing intense rainfall
rates and heavy/excessive rainfall will become more numerous
on Tuesday as height falls make their way out across Texas and as
the parent upper low ejects out over the Southern Plains. With
increasing flow off the Gulf drawing deeper moisture on-
shore....the convection should become increasingly efficient
rainfall makers.especially over portions of Louisiana and
Mississippi. There is still some differences in where models place
the heaviest rainfall...with the GFS and Canadian favoring a faster
solution while the EC/UK favoring the axis from eastern Texas into
northern Louisiana. This forecast cycle nudged the Moderate risk
area a bit eastward but not as far east as the GFS/Canadian.

Bann


Day 1 threat area: https://urldefense.com/v3/__https://www.wpc.ncep.noaa.go= v/qpf/94epoints.txt__;!!DZ3fjg!-EW9AHtRkqvBhglnX3TmBMdKeRmTLVaXns4Nn1w5mmb1= HSUH8n_kt78EBScZCxWzQ8LU31AabN3pgCOcmYGvE16f5G0$=20
Day 2 threat area: https://urldefense.com/v3/__https://www.wpc.ncep.noaa.go= v/qpf/98epoints.txt__;!!DZ3fjg!-EW9AHtRkqvBhglnX3TmBMdKeRmTLVaXns4Nn1w5mmb1= HSUH8n_kt78EBScZCxWzQ8LU31AabN3pgCOcmYGv1JyVYTQ$=20
Day 3 threat area: https://urldefense.com/v3/__https://www.wpc.ncep.noaa.go= v/qpf/99epoints.txt__;!!DZ3fjg!-EW9AHtRkqvBhglnX3TmBMdKeRmTLVaXns4Nn1w5mmb1= HSUH8n_kt78EBScZCxWzQ8LU31AabN3pgCOcmYGvEGmtMwQ$=20

=3D =3D =3D
To unsubscribe from WX-STORM and you already have a login, go to https://lists.illinois.edu and use the "Unsubscribe" link. Otherwise email Chris Novy at cnovy@cox.net and ask to be removed from WX-STORM.

--- SBBSecho 3.20-Linux
* Origin: capitolcityonline.net * Telnet/SSH:2022/HTTP (1:2320/105)

FOUS30 KWBC 042346
QPFERD

Excessive Rainfall Discussion
NWS Weather Prediction Center College Park MD
746 PM EDT Sun May 4 2025

Day 1
Valid 01Z Mon May 05 2025 - 12Z Mon May 05 2025

...THERE IS A SLIGHT RISK OF EXCESSIVE RAINFALL FOR PORTIONS OF
EASTERN NEW MEXICO...

Eastern New Mexico...
Heavy rainfall is expected through the evening hours near and north
of a slowly moving warm/quasi-stationary front. Precipitable water
values of 0.8-0.9", which is fairly saturated for that region,
combined with 500-1500 J/kg of MU CAPE and 25-50 kts of effective
bulk shear have been sufficient to develop organized thunderstorms.
Hourly rain amounts up to 1.5" with local totals up to 3" are=20
possible where cells merge, mesocyclones form, or storms backbuild.
The 18z HREF indicates heavy rain concerns are possible well into=20
the overnight hours, so the main adjustments were to expand the=20
Marginal Risk eastward and shift the Slight Risk southward to=20
account for the current instability pattern, which isn't expected=20
to extend any farther northward with time per the 22z RAP guidance.


Southwest...
In the vicinity of a deep layered low, thunderstorms have shifted
southeast with time from southeast CA and southern NV into AZ where
they are showing some cyclonic banding due to 500-1500 J/kg MU
CAPE, precipitable water values of 0.75" or so, and ~25 kts of
effective bulk shear. The 18z HREF guidance suggests a very slow
erosion of MU CAPE overnight, which should lead to continued=20
convective potential, though it should shrink in scale with time.=20
Hourly rain totals as high as 1.25" could lead to issues where=20
there are burn scars and dry washes/arroyos. The Marginal Risk=20
hoisted on the previous special issuance has been extended=20
southeast into AZ given ongoing radar trends and the signal seen in
the 18z HREF probabilities of 0.5"+. Local totals of 2" are=20
possible where cells train, merge, or backbuild/stall.


Northeast...
A deep layered low across the Ohio Valley combined with daytime
heating has led to convective development downwind/north of WV as
well as other sections of the northern Mid-Atlantic and southern
New England States. Precipitable water values up to 1", MU CAPE of
500-1500 J/kg, and effective bulk shear of 25-45 kts have led to=20
some convective banding across western PA with embedded=20
mesocyclones. Given the amount of moisture available, hourly rain=20
amounts to 1.5" and local totals to 3" are possible. Like the=20
Southwest, instability will be slow to erode so the convective=20
potential should slowly wane after sunset, with the guidance=20
indicating some new development in the early morning hours=20
downstream of where instability attempts to develop in and near the
Washington D.C. and New York City metropolitan area, with the=20
stronger signal near New York City. Some of the northern portion of
the previous Marginal Risk was removed given the decline of=20
instability across NY State and New England.

Roth


Day 2
Valid 12Z Mon May 05 2025 - 12Z Tue May 06 2025

...THERE IS A SLIGHT RISK OF EXCESSIVE RAINFALL OVER PORTIONS OF
THE SOUTHERN HIGH PLAINS...

...2030Z Update...

...Southern High Plains...

The Slight Risk area was expanded northwestward to include more of
the Texas Panhandle and far eastern New Mexico with this update and
in coordination with ABQ/Albuquerque, NM and AMA/Amarillo, TX
forecast offices. Showers and thunderstorms from the overnight
period will likely be ongoing along the NM/TX border at the start
of the period Monday morning, with periodic flareups of additional
convection expected throughout the day in this same area. Following
occasional daytime convection, a new MCS is likely to form during
the evening across west Texas and eastern NM and track northward
through the night. Thus, portions of the area, likely centered
around Lubbock/southern Texas Panhandle, will likely see multiple
rounds of heavy rain through Monday night. Soils in this area are
well above normal for moisture, especially for the eastern
Panhandle closer to Oklahoma. Therefore lesser amounts of rain than
normal will be needed to result in flash flooding.

...Northeast...

The Marginal Risk across portions of the Northeast was maintained
with few changes with this update. With coordination from
OKX/Upton, NY; ALY/Albany, NY; BOX/Taunton, MA; and PHI/Mt. Holly,
NJ forecast offices, a Slight Risk upgrade was considered for
portions of the area, with numerous models forecasting a swath of
1-2 inches of rain from NYC north and east through Long Island,
much of Connecticut, and the lower Hudson Valley and Catskills.
Despite that, very nominal instability and dry antecedent soils
conditions and low river levels were determined to likely prevent
much flash flooding outside of the most flood prone areas, so the
Marginal was maintained. Upslope will be a contributing factor to
locally heavier and steadier rain across Connecticut and the lower
Hudson Valley into the Catskills, but here too flash flooding
should be confined to only isolated areas. Should instability
increase or total rainfall increase a targeted Slight Risk may
still be needed with future updates.

Wegman

...Previous Discussion...

Texas into New Mexico...
A closed upper low over the Desert Southwest will continue to
meander eastward on Monday. Confidence remains in a focused area
for repeating heavy rainfall south from the TX Panhandle to the NM
border where a Slight Risk remains without many changes...with main
activity occurring once again around the time of maximum daytime
heating and then persisting into or through the night. The suite
of 04/00Z numerical guidance still shows the magnitude of
precipitable water values to exceed 2 sigma by 00Z Tuesday with the
1.25" precipitable water line reaching the Caprock. The 12Z QPF
consensus is for 2-4" over a sizable area just south of the TX
Panhandle...with locally higher amounts embedded in the broader QPF
area.

Mojave Desert through Southern Utah...
Numerous showers with embedded daytime and evening thunderstorms is
still expected as upper low continues to meander over Arizona as
it begins to fill. Moisture is still anomalous for this time of
year...being some 2 to 3 standardized anomalies above climatology
for early May...but concern would be greater for excessive rainfall
if the actual values of precipitable water values were greater and
intense rainfall rates would be sustained for a longer duration.
As a result...the risk of excessive rainfall appears to be non-zero
but not enough to warrant a Marginal risk area based on
coordination with local offices.

Northern Mid-Atlantic into southern New England...
Closed low will continue to meanders across portions of the Upper
OH Valley through Monday night. Continued onshore flow brings the
threat for repeating locally heavy rain over the northern Mid-
Atlantic into southern New England which will have seen some heavy
rain between now and then. A Marginal Risk is maintained.


Bann

Day 3
Valid 12Z Tue May 06 2025 - 12Z Wed May 07 2025

...THERE IS A MODERATE RISK OF EXCESSIVE RAINFALL OVER PORTIONS OF
THE SOUTHERN MISSISSIPPI VALLEY/CENTRAL GULF COAST REGION...

...2030Z Update...

...Lower Mississippi Valley to the Colorado Front Range...

The inherited Moderate Risk area was greatly expanded with this
update, in keeping with numerous pieces of guidance, ensembles, and
means all favoring a significant thunderstorm training and heavy
rain event across the Arklatex and into central Mississippi. The
RRFS suggests multiple lines of storms will cross west to east
across the Moderate Risk area, starting in the north from northeast
Texas, along the Louisiana/Arkansas border, and then continuing
into Mississippi. The trailing (southwestern) portion of the line
will hang back as it is joined by additional storms over southeast
Texas that progress eastward.

The first line will start out at roughly a southwest to northeast
orientation, however, into Tuesday night, the lines will get
progressively more west-east oriented, meaning greater chance that
repeating lines of storms will move across Louisiana. Meanwhile the
outflow on the northern side of the complex of storms will allow
for continued lighter rains in northern areas that were hard hit
earlier in the evening, which will continue or worsen ongoing flash
flooding as a result of the earlier storms. While the RRFS is far
from a perfect solution as to who will get heavy rain and when,
given the footprint of heavy rain in the RRFS is at least similar
and in a roughly the same location as the heavy rain footprint in
the global models, it appeared to offer a good first guess as to
how the storm evolution will play out through the period.

The Moderate Risk area remains a lower-end Moderate for now until
there is better consensus (and likely southward shifts) in the area
of heaviest rainfall. By then it's possible portions of the area
may be considered in a higher-end Moderate Risk. For now...rainfall
amounts in this area should not reach High Risk levels, since there
is at least some southward movement for most of the storms with
time, so no one area sees heavy rains for an extended duration.
Further, it's possible that the training storms end up offshore of
the Louisiana coast should there be more dramatic southward shifts,
so the Moderate Risk was determined to be the appropriate risk
level for flash flooding. Should there be significant increases
with future runs, that are expected to be more concentrated, then
it's not completely out of the question that a targeted High Risk
may be needed with future updates.

While the heaviest rains will be associated with the moderate Risk
area in portions of the lower Mississippi Valley, a good amount of
that moisture and instability will be drawn northwestward ahead of
a strong shortwave trough associated with the slow-moving upper
level low over the 4 Corners region. This will extend an area of
heavy rain from the MCS/Moderate Risk region northwest across much
of Oklahoma and into southern Colorado. This in turn will lead to a
shearing front, but the heavy rainfall will be moving over areas
hard hit with prior flooding rains, particularly over Oklahoma and
the Panhandles. Thus, the Slight Risk extends well west into
southeastern Colorado, where upslope may play a role in producing
locally heavy rains along the Front Range, while the higher
elevations pick up heavy snow.

...Northeast...

A slow moving upper level low over the Midwest will continue to
pump Atlantic moisture into New England on Tuesday...a continuation
of periods of rain from the same system both today and on Monday.
By Tuesday, however, instability into and south of New England
will increase to up to 500 J/kg. While this amount of instability
is far from impressive, it will still be enough to allow for
convective showers and maybe some embedded thunderstorms to move
north up the coast and into New England. Antecedent soil moisture
conditions are likely to be significantly more favorable for the
development of flash flooding in this region considering the rain
expected there today through Monday. Thus, a Slight Risk upgrade is
possible in this area assuming there are increases in the forecast
rainfall once this period moves into the short-term and the CAMs
can analyze the system.

Wegman

...Previous Discussion...

Showers and thunderstorms capable of producing intense rainfall
rates and heavy/excessive rainfall will become more numerous
on Tuesday as height falls make their way out across Texas and as
the parent upper low ejects out over the Southern Plains. With
increasing flow off the Gulf drawing deeper moisture on-
shore....the convection should become increasingly efficient
rainfall makers.especially over portions of Louisiana and
Mississippi. There is still some differences in where models place
the heaviest rainfall...with the GFS and Canadian favoring a faster
solution while the EC/UK favoring the axis from eastern Texas into
northern Louisiana. This forecast cycle nudged the Moderate risk
area a bit eastward but not as far east as the GFS/Canadian.

Bann


Day 1 threat area: https://urldefense.com/v3/__https://www.wpc.ncep.noaa.go= v/qpf/94epoints.txt__;!!DZ3fjg!8dldfN7hTUzwil4TeDjnY_oyM5SDS0-V_iBWl8aQuGkh= JRTHDk0feO5qhrjXK3a-vWg_0-39Bqe0W9TltdbuGkUjfOo$=20
Day 2 threat area: https://urldefense.com/v3/__https://www.wpc.ncep.noaa.go= v/qpf/98epoints.txt__;!!DZ3fjg!8dldfN7hTUzwil4TeDjnY_oyM5SDS0-V_iBWl8aQuGkh= JRTHDk0feO5qhrjXK3a-vWg_0-39Bqe0W9TltdbuTSaoDJM$=20
Day 3 threat area: https://urldefense.com/v3/__https://www.wpc.ncep.noaa.go= v/qpf/99epoints.txt__;!!DZ3fjg!8dldfN7hTUzwil4TeDjnY_oyM5SDS0-V_iBWl8aQuGkh= JRTHDk0feO5qhrjXK3a-vWg_0-39Bqe0W9Tltdbu8E4-bPw$=20

=3D =3D =3D
To unsubscribe from WX-STORM and you already have a login, go to https://lists.illinois.edu and use the "Unsubscribe" link. Otherwise email Chris Novy at cnovy@cox.net and ask to be removed from WX-STORM.

--- SBBSecho 3.20-Linux
* Origin: capitolcityonline.net * Telnet/SSH:2022/HTTP (1:2320/105)

FOUS30 KWBC 050828
QPFERD

Excessive Rainfall Discussion
NWS Weather Prediction Center College Park MD
428 AM EDT Mon May 5 2025

Day 1
Valid 12Z Mon May 05 2025 - 12Z Tue May 06 2025

..THERE IS A SLIGHT RISK OF EXCESSIVE RAINFALL OVER PORTIONS OF
THE SOUTHERN HIGH PLAINS...

...Southern High Plains...
Showers and thunderstorms capable of producing downpours and a risk
of excessive rainfall will become more numerous during the day
across parts of New Mexico that spreads south and east into parts
of western Texas later in the day and overnight as moisture deepens
and mid/upper height falls eject out over the plains with an MCS=20
likely to form during the evening across west Texas/easter New
Mexico. Given antecedent conditions and soils...thinking is that
this is a higher-end Slight risk over parts of Texas ls in this=20
area are well above normal for moisture, especially for the eastern
Panhandle closer to Oklahoma. Therefore lesser amounts of rain=20
than normal will be needed to result in flash flooding. There was
little need to make more than minor adjustments to the previously-
issued ERO.

...Northeast...
There is a continuing risk of excessive rainfall as a closed low
meanders over parts of the Ohio Valley and Great Lakes
region...leaving the Northeast US under diffluent flow at upper
levels while moisture continues to be transported into the region=20
at low levels. Now that there has been an increase in model QPF=20
from the global models and some signals from the HREF for 3 hr QPF=20
of 2+ inches in parts of southern NY and coastal Southern New=20 England...hoisted a Slight Risk area there. The coverage extended a
bit northward and westward to cover areas that received 1.5 to=20
2.75 inches on Sunday. However...the area has been dry for a while=20
and stream flows are generally low which should help mitigate the=20
flash flood risk over a broad area. The Marginal risk area=20
surrounding the Slight was expanded a bit northward but was at=20
least comparable with previous outlooks.

...Southwest...
There is a Marginal risk of excessive rainfall over portions of the
Southwest US as a deep layered upper low moves very slowly=20
eastward. Between precipitable water values of 0.5 to 0.75 inches=20
and cold temperatures aloft helping to create steep low/mid level=20
lapse rates...another round of scattered to numerous showers and=20 thunderstorms should develop again with isolated downpours and=20
locally heavy rainfall amounts today.

Bann


Day 2
Valid 12Z Tue May 06 2025 - 12Z Wed May 07 2025

...THERE IS A MODERATE RISK OF EXCESSIVE RAINFALL OVER PORTIONS OF
THE SOUTHERN MISSISSIPPI VALLEY/CENTRAL GULF COAST REGION...

...Lower Mississippi Valley to the Colorado Front Range...

The inherited Moderate Risk area was greatly expanded with this
update as global models get a better handle on instability and part
of the event begins to be covered by high resolution CAMs.
Heaviest rainfall and associated risk of flash flooding should be=20
tied to deeper convection that forms and moves from parts of
eastern Texas across central and northern Louisiana/far southern=20
Arkansas into parts of Mississippi. 05/00Z guidance continued to=20
depict amounts of 2 to 4 inches in the area with embedded amounts=20
greater than 6 inches. Convection should start out at roughly a=20
southwest to northeast orientation but become realigned more west
to east Tuesday night. This increases the potential for repeating=20
storms and training of cells. On the northern side of the complex=20
of storms will allow for continued lighter rains in northern areas=20
that were hard hit earlier in the evening, which will continue or=20
worsen ongoing flash flooding as a result of the earlier storms.=20
Should there be significant increases with future runs, that are=20
expected to be more concentrated, then it's not completely out of=20
the question that a targeted High Risk may be needed with future=20
updates.

Even though the heaviest rains will be associated with the=20
moderate Risk area in portions of the lower Mississippi Valley, a=20
good amount of that moisture and instability will be drawn=20
northwestward ahead of a strong shortwave trough associated with=20
the slow-moving upper level low over the 4 Corners region with some
of the heavier rainfall amounts moving over areas hard hit with=20
prior flooding rains, particularly over Oklahoma and the=20
Panhandles.=20

...Northeast...

A slow moving upper level low over the Midwest will continue to
pump Atlantic moisture into New England on Tuesday...a continuation
of periods of rain from today. Instability is far from impressive,
but it will still be enough to allow for convective showers and=20
maybe some embedded thunderstorms to move north up the coast and=20
into New England but model QPF remained in check given the
progressive nature of the forcing.=20

Bann whether or not the

Day 3
Valid 12Z Wed May 07 2025 - 12Z Thu May 08 2025

...THERE IS A SLIGHT RISK OF EXCESSIVE OVER PORTIONS OF THE GULF
COAST...

Locally heavy rainfall looks to be lingering along portions of the
Gulf coast and Upper Texas coast. Most of the rainfall should be
along and south of a cold front left behind by the system that
brought heavy to excessive rainfall to the area on Tuesday. Even
after the cold passes south over the waters of the Gulf...broad
isentropic upglide from broad southwesterly flow should keep at=20
least as risk of rain. However...the 00Z suite of guidance=20
suggested that the convection may be more widely scattered and more
offshore than shown by the 01Z and 05Z NBM and may end. Later=20
outlooks will keep an eye on whether this trend continues.


Bann


Day 1 threat area: https://urldefense.com/v3/__https://www.wpc.ncep.noaa.go= v/qpf/94epoints.txt__;!!DZ3fjg!8EM5fHwrHovSnVcwc8fa1U_drTVY9K9Z1f99pUL3QwlM= IM9iFEnNbDirR6jtq_TyefNM-qZxNzlLicBw3RsNCtTj-T0$=20
Day 2 threat area: https://urldefense.com/v3/__https://www.wpc.ncep.noaa.go= v/qpf/98epoints.txt__;!!DZ3fjg!8EM5fHwrHovSnVcwc8fa1U_drTVY9K9Z1f99pUL3QwlM= IM9iFEnNbDirR6jtq_TyefNM-qZxNzlLicBw3RsN8GfnL7c$=20
Day 3 threat area: https://urldefense.com/v3/__https://www.wpc.ncep.noaa.go= v/qpf/99epoints.txt__;!!DZ3fjg!8EM5fHwrHovSnVcwc8fa1U_drTVY9K9Z1f99pUL3QwlM= IM9iFEnNbDirR6jtq_TyefNM-qZxNzlLicBw3RsNO-4IAJ0$=20

=3D =3D =3D
To unsubscribe from WX-STORM and you already have a login, go to https://lists.illinois.edu and use the "Unsubscribe" link. Otherwise email Chris Novy at cnovy@cox.net and ask to be removed from WX-STORM.

--- SBBSecho 3.20-Linux
* Origin: capitolcityonline.net * Telnet/SSH:2022/HTTP (1:2320/105)

FOUS30 KWBC 051618
QPFERD

Excessive Rainfall Discussion
NWS Weather Prediction Center College Park MD
1218 PM EDT Mon May 5 2025

Day 1
Valid 16Z Mon May 05 2025 - 12Z Tue May 06 2025

..THERE IS A SLIGHT RISK OF EXCESSIVE RAINFALL OVER PORTIONS OF
THE SOUTHERN HIGH PLAINS...

16z Update: Generally only minor changes to the inherited risk=20
areas with this update. The Slight risk over the Southern Plains=20
was expanded west into more of eastern NM based on guidance trends.
Convection with locally high rates should expand over eastern NM=20
between 00z-06z this evening.

The Marginal risk was expanded to the TX coast to account for=20
ongoing convection over south central TX. Guidance differs on the=20
evolution of this activity, but some chance for at least modest=20
upscale growth into a convective cluster or two that could result=20
in localized flash flooding.=20

A Marginal risk was also expanded southward into more of central=20
and eastern VA. Clearing skies will result in isolated to scattered
convective development over this area by this afternoon. Cells=20
might tend to move along quick enough to prevent FFG exceedance=20
(with FFG quite high), but the rainfall will be efficient and=20
cells will be capable of dropping a quick 2" on a localized basis.=20
So while it generally probably won't cause more than flood=20
advisory type impacts, if a heavier cells moves over an urban area
could certainly see an isolated flash flood.

Chenard

...Previous Discussion...

...Southern High Plains...
Showers and thunderstorms capable of producing downpours and a risk
of excessive rainfall will become more numerous during the day
across parts of New Mexico that spreads south and east into parts
of western Texas later in the day and overnight as moisture deepens
and mid/upper height falls eject out over the plains with an MCS
likely to form during the evening across west Texas/easter New
Mexico. Given antecedent conditions and soils...thinking is that
this is a higher-end Slight risk over parts of Texas ls in this
area are well above normal for moisture, especially for the eastern
Panhandle closer to Oklahoma. Therefore lesser amounts of rain
than normal will be needed to result in flash flooding. There was
little need to make more than minor adjustments to the previously-
issued ERO.

...Northeast...
There is a continuing risk of excessive rainfall as a closed low
meanders over parts of the Ohio Valley and Great Lakes
region...leaving the Northeast US under diffluent flow at upper
levels while moisture continues to be transported into the region
at low levels. Now that there has been an increase in model QPF
from the global models and some signals from the HREF for 3 hr QPF
of 2+ inches in parts of southern NY and coastal Southern New
England...hoisted a Slight Risk area there. The coverage extended a
bit northward and westward to cover areas that received 1.5 to
2.75 inches on Sunday. However...the area has been dry for a while
and stream flows are generally low which should help mitigate the
flash flood risk over a broad area. The Marginal risk area
surrounding the Slight was expanded a bit northward but was at
least comparable with previous outlooks.

...Southwest...
There is a Marginal risk of excessive rainfall over portions of the
Southwest US as a deep layered upper low moves very slowly
eastward. Between precipitable water values of 0.5 to 0.75 inches
and cold temperatures aloft helping to create steep low/mid level
lapse rates...another round of scattered to numerous showers and
thunderstorms should develop again with isolated downpours and
locally heavy rainfall amounts today.

Bann


Day 2
Valid 12Z Tue May 06 2025 - 12Z Wed May 07 2025

...THERE IS A MODERATE RISK OF EXCESSIVE RAINFALL OVER PORTIONS OF
THE SOUTHERN MISSISSIPPI VALLEY/CENTRAL GULF COAST REGION...

...Lower Mississippi Valley to the Colorado Front Range...

The inherited Moderate Risk area was greatly expanded with this
update as global models get a better handle on instability and part
of the event begins to be covered by high resolution CAMs.
Heaviest rainfall and associated risk of flash flooding should be
tied to deeper convection that forms and moves from parts of
eastern Texas across central and northern Louisiana/far southern
Arkansas into parts of Mississippi. 05/00Z guidance continued to
depict amounts of 2 to 4 inches in the area with embedded amounts
greater than 6 inches. Convection should start out at roughly a
southwest to northeast orientation but become realigned more west
to east Tuesday night. This increases the potential for repeating
storms and training of cells. On the northern side of the complex
of storms will allow for continued lighter rains in northern areas
that were hard hit earlier in the evening, which will continue or
worsen ongoing flash flooding as a result of the earlier storms.
Should there be significant increases with future runs, that are
expected to be more concentrated, then it's not completely out of
the question that a targeted High Risk may be needed with future
updates.

Even though the heaviest rains will be associated with the
moderate Risk area in portions of the lower Mississippi Valley, a
good amount of that moisture and instability will be drawn
northwestward ahead of a strong shortwave trough associated with
the slow-moving upper level low over the 4 Corners region with some
of the heavier rainfall amounts moving over areas hard hit with
prior flooding rains, particularly over Oklahoma and the
Panhandles.

...Northeast...

A slow moving upper level low over the Midwest will continue to
pump Atlantic moisture into New England on Tuesday...a continuation
of periods of rain from today. Instability is far from impressive,
but it will still be enough to allow for convective showers and
maybe some embedded thunderstorms to move north up the coast and
into New England but model QPF remained in check given the
progressive nature of the forcing.

Bann whether or not the

Day 3
Valid 12Z Wed May 07 2025 - 12Z Thu May 08 2025

...THERE IS A SLIGHT RISK OF EXCESSIVE OVER PORTIONS OF THE GULF
COAST...

Locally heavy rainfall looks to be lingering along portions of the
Gulf coast and Upper Texas coast. Most of the rainfall should be
along and south of a cold front left behind by the system that
brought heavy to excessive rainfall to the area on Tuesday. Even
after the cold passes south over the waters of the Gulf...broad
isentropic upglide from broad southwesterly flow should keep at
least as risk of rain. However...the 00Z suite of guidance
suggested that the convection may be more widely scattered and more
offshore than shown by the 01Z and 05Z NBM and may end. Later
outlooks will keep an eye on whether this trend continues.


Bann


Day 1 threat area: https://urldefense.com/v3/__https://www.wpc.ncep.noaa.go= v/qpf/94epoints.txt__;!!DZ3fjg!_yU60z1h_X0KV3xQwVrtR3NZbE7uQ4VHEAsbVPL7WdIx= udmrzlpQM8jC_4W7_Ecutu6QYOBPWrEHAf9hc1eEwPGpCbw$=20
Day 2 threat area: https://urldefense.com/v3/__https://www.wpc.ncep.noaa.go= v/qpf/98epoints.txt__;!!DZ3fjg!_yU60z1h_X0KV3xQwVrtR3NZbE7uQ4VHEAsbVPL7WdIx= udmrzlpQM8jC_4W7_Ecutu6QYOBPWrEHAf9hc1eEJ-YFKEk$=20
Day 3 threat area: https://urldefense.com/v3/__https://www.wpc.ncep.noaa.go= v/qpf/99epoints.txt__;!!DZ3fjg!_yU60z1h_X0KV3xQwVrtR3NZbE7uQ4VHEAsbVPL7WdIx= udmrzlpQM8jC_4W7_Ecutu6QYOBPWrEHAf9hc1eEm60xumM$=20

=3D =3D =3D
To unsubscribe from WX-STORM and you already have a login, go to https://lists.illinois.edu and use the "Unsubscribe" link. Otherwise email Chris Novy at cnovy@cox.net and ask to be removed from WX-STORM.

--- SBBSecho 3.20-Linux
* Origin: capitolcityonline.net * Telnet/SSH:2022/HTTP (1:2320/105)

FOUS30 KWBC 052001
QPFERD

Excessive Rainfall Discussion
NWS Weather Prediction Center College Park MD
401 PM EDT Mon May 5 2025

Day 1
Valid 16Z Mon May 05 2025 - 12Z Tue May 06 2025

..THERE IS A SLIGHT RISK OF EXCESSIVE RAINFALL OVER PORTIONS OF
THE SOUTHERN HIGH PLAINS...

16z Update: Generally only minor changes to the inherited risk
areas with this update. The Slight risk over the Southern Plains
was expanded west into more of eastern NM based on guidance trends.
Convection with locally high rates should expand over eastern NM
between 00z-06z this evening.

The Marginal risk was expanded to the TX coast to account for
ongoing convection over south central TX. Guidance differs on the
evolution of this activity, but some chance for at least modest
upscale growth into a convective cluster or two that could result
in localized flash flooding.

A Marginal risk was also expanded southward into more of central
and eastern VA. Clearing skies will result in isolated to scattered
convective development over this area by this afternoon. Cells
might tend to move along quick enough to prevent FFG exceedance
(with FFG quite high), but the rainfall will be efficient and
cells will be capable of dropping a quick 2" on a localized basis.
So while it generally probably won't cause more than flood
advisory type impacts, if a heavier cells moves over an urban area
could certainly see an isolated flash flood.

Chenard

...Previous Discussion...

...Southern High Plains...
Showers and thunderstorms capable of producing downpours and a risk
of excessive rainfall will become more numerous during the day
across parts of New Mexico that spreads south and east into parts
of western Texas later in the day and overnight as moisture deepens
and mid/upper height falls eject out over the plains with an MCS
likely to form during the evening across west Texas/easter New
Mexico. Given antecedent conditions and soils...thinking is that
this is a higher-end Slight risk over parts of Texas ls in this
area are well above normal for moisture, especially for the eastern
Panhandle closer to Oklahoma. Therefore lesser amounts of rain
than normal will be needed to result in flash flooding. There was
little need to make more than minor adjustments to the previously-
issued ERO.

...Northeast...
There is a continuing risk of excessive rainfall as a closed low
meanders over parts of the Ohio Valley and Great Lakes
region...leaving the Northeast US under diffluent flow at upper
levels while moisture continues to be transported into the region
at low levels. Now that there has been an increase in model QPF
from the global models and some signals from the HREF for 3 hr QPF
of 2+ inches in parts of southern NY and coastal Southern New
England...hoisted a Slight Risk area there. The coverage extended a
bit northward and westward to cover areas that received 1.5 to
2.75 inches on Sunday. However...the area has been dry for a while
and stream flows are generally low which should help mitigate the
flash flood risk over a broad area. The Marginal risk area
surrounding the Slight was expanded a bit northward but was at
least comparable with previous outlooks.

...Southwest...
There is a Marginal risk of excessive rainfall over portions of the
Southwest US as a deep layered upper low moves very slowly
eastward. Between precipitable water values of 0.5 to 0.75 inches
and cold temperatures aloft helping to create steep low/mid level
lapse rates...another round of scattered to numerous showers and
thunderstorms should develop again with isolated downpours and
locally heavy rainfall amounts today.

Bann


Day 2
Valid 12Z Tue May 06 2025 - 12Z Wed May 07 2025

...THERE IS A MODERATE RISK OF EXCESSIVE RAINFALL OVER PORTIONS OF
EASTERN TEXAS INTO THE LOWER MISSISSIPPI VALLEY...

20z Update:
Main adjustment was a southward shift of the MDT risk over eastern
TX into the lower MS Valley based on trends seen in the 12z HREF
and REFS. Highest 3" EAS probabilities (a smoothed point
probability) stretch from east TX into much of LA, with 5"
neighborhood probabilities getting into the 30-70% range. Thus
seems likely that a swath of 3-5" of rainfall will occur, with
localized totals over 6". 8" neighborhood probabilities drop to 20%
or less, with the forward progression potentially limiting the
exceedance of 8" and keeping this from being a High risk type of
event. Nonetheless, even with a progressive system convection will
be organized and widespread enough to result in significant=20
rainfall totals, especially given what should be a very efficient=20 environment for high rates. Numerous instances of flash flooding=20
are expected, some of which could be locally significant in nature,
especially if these higher totals end up over a more sensitive=20
urban area.

Chenard

...Previous Discussion...

...Lower Mississippi Valley to the Colorado Front Range...

The inherited Moderate Risk area was greatly expanded with this
update as global models get a better handle on instability and part
of the event begins to be covered by high resolution CAMs.
Heaviest rainfall and associated risk of flash flooding should be
tied to deeper convection that forms and moves from parts of
eastern Texas across central and northern Louisiana/far southern
Arkansas into parts of Mississippi. 05/00Z guidance continued to
depict amounts of 2 to 4 inches in the area with embedded amounts
greater than 6 inches. Convection should start out at roughly a
southwest to northeast orientation but become realigned more west
to east Tuesday night. This increases the potential for repeating
storms and training of cells. On the northern side of the complex
of storms will allow for continued lighter rains in northern areas
that were hard hit earlier in the evening, which will continue or
worsen ongoing flash flooding as a result of the earlier storms.
Should there be significant increases with future runs, that are
expected to be more concentrated, then it's not completely out of
the question that a targeted High Risk may be needed with future
updates.

Even though the heaviest rains will be associated with the
moderate Risk area in portions of the lower Mississippi Valley, a
good amount of that moisture and instability will be drawn
northwestward ahead of a strong shortwave trough associated with
the slow-moving upper level low over the 4 Corners region with some
of the heavier rainfall amounts moving over areas hard hit with
prior flooding rains, particularly over Oklahoma and the
Panhandles.

...Northeast...

A slow moving upper level low over the Midwest will continue to
pump Atlantic moisture into New England on Tuesday...a continuation
of periods of rain from today. Instability is far from impressive,
but it will still be enough to allow for convective showers and
maybe some embedded thunderstorms to move north up the coast and
into New England but model QPF remained in check given the
progressive nature of the forcing.

Bann

Day 3
Valid 12Z Wed May 07 2025 - 12Z Thu May 08 2025

...THERE IS A SLIGHT RISK OF EXCESSIVE OVER PORTIONS OF THE GULF
COAST...

20z Update:
Only minimal changes to the inherited Slight risk over southeast TX
into LA. The environment remains conducive for potential training
convection early Wednesday, but some question whether this activity
ends up just offshore or stays onshore. Our latest WPC
deterministic QPF would support a MDT risk over LA...however
several pieces of guidance are trending towards a more offshore
solution by this time...including the AIFS and the 12z RRFS. Given
this uncertainty we will leave the risk at a Slight level for now.
Either way these areas of coastal TX into LA have a flash flood=20
risk...just a question as to whether the main risk is late on day 2
or on day 3. Future shifts will be able to continue to fine tune=20
these timing details.

Chenard

...Previous Discussion...

Locally heavy rainfall looks to be lingering along portions of the
Gulf coast and Upper Texas coast. Most of the rainfall should be
along and south of a cold front left behind by the system that
brought heavy to excessive rainfall to the area on Tuesday. Even
after the cold passes south over the waters of the Gulf...broad
isentropic upglide from broad southwesterly flow should keep at
least as risk of rain. However...the 00Z suite of guidance
suggested that the convection may be more widely scattered and more
offshore than shown by the 01Z and 05Z NBM and may end. Later
outlooks will keep an eye on whether this trend continues.


Bann


Day 1 threat area: https://urldefense.com/v3/__https://www.wpc.ncep.noaa.go= v/qpf/94epoints.txt__;!!DZ3fjg!8WhsDe7rf9lil0b4xpG8SrJkL7j416u5TIk6or4MXaHO= m1xd75LonOxXM_QPGN8lFmXoeeQ_i2QFhHiD6l86eu2gnxw$=20
Day 2 threat area: https://urldefense.com/v3/__https://www.wpc.ncep.noaa.go= v/qpf/98epoints.txt__;!!DZ3fjg!8WhsDe7rf9lil0b4xpG8SrJkL7j416u5TIk6or4MXaHO= m1xd75LonOxXM_QPGN8lFmXoeeQ_i2QFhHiD6l86hHonIAI$=20
Day 3 threat area: https://urldefense.com/v3/__https://www.wpc.ncep.noaa.go= v/qpf/99epoints.txt__;!!DZ3fjg!8WhsDe7rf9lil0b4xpG8SrJkL7j416u5TIk6or4MXaHO= m1xd75LonOxXM_QPGN8lFmXoeeQ_i2QFhHiD6l86bNfhgaU$=20

=3D =3D =3D
To unsubscribe from WX-STORM and you already have a login, go to https://lists.illinois.edu and use the "Unsubscribe" link. Otherwise email Chris Novy at cnovy@cox.net and ask to be removed from WX-STORM.

--- SBBSecho 3.20-Linux
* Origin: capitolcityonline.net * Telnet/SSH:2022/HTTP (1:2320/105)

FOUS30 KWBC 060030
QPFERD

Excessive Rainfall Discussion
NWS Weather Prediction Center College Park MD
830 PM EDT Mon May 5 2025

Day 1
Valid 01Z Tue May 06 2025 - 12Z Tue May 06 2025

..THERE IS A SLIGHT RISK OF EXCESSIVE RAINFALL OVER PORTIONS OF
THE SOUTHERN HIGH PLAINS...

...Southern High Plains...
Showers and thunderstorms capable of producing downpours and a risk
of excessive rainfall will become more numerous across parts of=20
eastern New Mexico and spread south and east into parts of western
Texas as moisture deepens within an upslope flow regime and=20
an upper low and surrounding shortwaves approach the region.
With precipitable water values ranging from 0.75" in the Southern=20
High Plains to 1.5" at lower elevations to the east, a broad area=20
of 500-3000 J/kg of MU CAPE to the south, and effective bulk shear=20
of 40-70 kts, supercell development is likely to continue. An MCS=20
likely to form tonight as storms merge into a broader mass across=20
western Texas/eastern New Mexico. Hourly rain totals to 2.5" would
be possible where storms backbuild, merge, or try to train, with=20
local totals to 5" possible given the non-zero probabilities of=20
such within the 18z HREF guidance. The signal in the 18z HREF=20
probabilities of the various precipitation thresholds through 12z=20
has shifted southward, which led to a southward shift in the Slight
Risk area. Radar reflectivity and MU CAPE trends in southeast TX
were also taken into account with the adjustments made to the
Marginal Risk area.


...Northeast...
There is a continuing risk of excessive rainfall as a closed low
meanders over parts of the Ohio Valley and Great Lakes
region...leaving the Northeast under diffluent flow at upper=20
levels while moisture continues to be transported into the region=20
at low levels. Adjustments were made to account for radar
reflectivity trends and 18z HREF probabilities of various
thresholds.


...Southwest...
There is a Marginal risk of excessive rainfall over portions of the
Southwest US as a deep layered upper low moves very slowly
eastward. Between precipitable water values of 0.5 to 0.75 inches
and cold temperatures aloft helping to create steep low/mid level
lapse rates and saturated profiles...showers and thunderstorms=20
should continue into tonight with isolated downpours and locally=20
heavy rainfall amounts today. Adjustments were made to account for
radar reflectivity trends and 18z HREF probabilities of various=20
thresholds.

Roth/Bann


Day 2
Valid 12Z Tue May 06 2025 - 12Z Wed May 07 2025

...THERE IS A MODERATE RISK OF EXCESSIVE RAINFALL OVER PORTIONS OF
EASTERN TEXAS INTO THE LOWER MISSISSIPPI VALLEY...

20z Update:
Main adjustment was a southward shift of the MDT risk over eastern
TX into the lower MS Valley based on trends seen in the 12z HREF
and REFS. Highest 3" EAS probabilities (a smoothed point
probability) stretch from east TX into much of LA, with 5"
neighborhood probabilities getting into the 30-70% range. Thus
seems likely that a swath of 3-5" of rainfall will occur, with
localized totals over 6". 8" neighborhood probabilities drop to 20%
or less, with the forward progression potentially limiting the
exceedance of 8" and keeping this from being a High risk type of
event. Nonetheless, even with a progressive system convection will
be organized and widespread enough to result in significant
rainfall totals, especially given what should be a very efficient
environment for high rates. Numerous instances of flash flooding
are expected, some of which could be locally significant in nature,
especially if these higher totals end up over a more sensitive
urban area.

Chenard

...Previous Discussion...

...Lower Mississippi Valley to the Colorado Front Range...

The inherited Moderate Risk area was greatly expanded with this
update as global models get a better handle on instability and part
of the event begins to be covered by high resolution CAMs.
Heaviest rainfall and associated risk of flash flooding should be
tied to deeper convection that forms and moves from parts of
eastern Texas across central and northern Louisiana/far southern
Arkansas into parts of Mississippi. 05/00Z guidance continued to
depict amounts of 2 to 4 inches in the area with embedded amounts
greater than 6 inches. Convection should start out at roughly a
southwest to northeast orientation but become realigned more west
to east Tuesday night. This increases the potential for repeating
storms and training of cells. On the northern side of the complex
of storms will allow for continued lighter rains in northern areas
that were hard hit earlier in the evening, which will continue or
worsen ongoing flash flooding as a result of the earlier storms.
Should there be significant increases with future runs, that are
expected to be more concentrated, then it's not completely out of
the question that a targeted High Risk may be needed with future
updates.

Even though the heaviest rains will be associated with the
moderate Risk area in portions of the lower Mississippi Valley, a
good amount of that moisture and instability will be drawn
northwestward ahead of a strong shortwave trough associated with
the slow-moving upper level low over the 4 Corners region with some
of the heavier rainfall amounts moving over areas hard hit with
prior flooding rains, particularly over Oklahoma and the
Panhandles.

...Northeast...

A slow moving upper level low over the Midwest will continue to
pump Atlantic moisture into New England on Tuesday...a continuation
of periods of rain from today. Instability is far from impressive,
but it will still be enough to allow for convective showers and
maybe some embedded thunderstorms to move north up the coast and
into New England but model QPF remained in check given the
progressive nature of the forcing.

Bann

Day 3
Valid 12Z Wed May 07 2025 - 12Z Thu May 08 2025

...THERE IS A SLIGHT RISK OF EXCESSIVE OVER PORTIONS OF THE GULF
COAST...

20z Update:
Only minimal changes to the inherited Slight risk over southeast TX
into LA. The environment remains conducive for potential training
convection early Wednesday, but some question whether this activity
ends up just offshore or stays onshore. Our latest WPC
deterministic QPF would support a MDT risk over LA...however
several pieces of guidance are trending towards a more offshore
solution by this time...including the AIFS and the 12z RRFS. Given
this uncertainty we will leave the risk at a Slight level for now.
Either way these areas of coastal TX into LA have a flash flood
risk...just a question as to whether the main risk is late on day 2
or on day 3. Future shifts will be able to continue to fine tune
these timing details.

Chenard

...Previous Discussion...

Locally heavy rainfall looks to be lingering along portions of the
Gulf coast and Upper Texas coast. Most of the rainfall should be
along and south of a cold front left behind by the system that
brought heavy to excessive rainfall to the area on Tuesday. Even
after the cold passes south over the waters of the Gulf...broad
isentropic upglide from broad southwesterly flow should keep at
least as risk of rain. However...the 00Z suite of guidance
suggested that the convection may be more widely scattered and more
offshore than shown by the 01Z and 05Z NBM and may end. Later
outlooks will keep an eye on whether this trend continues.


Bann


Day 1 threat area: https://urldefense.com/v3/__https://www.wpc.ncep.noaa.go= v/qpf/94epoints.txt__;!!DZ3fjg!5xU1V2FDVGNwyqLiXaGlYjGNXT8W033uo4Hlg14IaqZq= Nv4zVFlqudizb2Wizd9WD3D9hKr0pR3s2Wdg8uRNJhFcPIo$=20
Day 2 threat area: https://urldefense.com/v3/__https://www.wpc.ncep.noaa.go= v/qpf/98epoints.txt__;!!DZ3fjg!5xU1V2FDVGNwyqLiXaGlYjGNXT8W033uo4Hlg14IaqZq= Nv4zVFlqudizb2Wizd9WD3D9hKr0pR3s2Wdg8uRNk41atAs$=20
Day 3 threat area: https://urldefense.com/v3/__https://www.wpc.ncep.noaa.go= v/qpf/99epoints.txt__;!!DZ3fjg!5xU1V2FDVGNwyqLiXaGlYjGNXT8W033uo4Hlg14IaqZq= Nv4zVFlqudizb2Wizd9WD3D9hKr0pR3s2Wdg8uRNmw-oLoM$=20

=3D =3D =3D
To unsubscribe from WX-STORM and you already have a login, go to https://lists.illinois.edu and use the "Unsubscribe" link. Otherwise email Chris Novy at cnovy@cox.net and ask to be removed from WX-STORM.

--- SBBSecho 3.20-Linux
* Origin: capitolcityonline.net * Telnet/SSH:2022/HTTP (1:2320/105)

FOUS30 KWBC 060812
QPFERD

Excessive Rainfall Discussion
NWS Weather Prediction Center College Park MD
412 AM EDT Tue May 6 2025

Day 1
Valid 12Z Tue May 06 2025 - 12Z Wed May 07 2025

...THERE IS A MODERATE RISK OF EXCESSIVE RAINFALL OVER PORTIONS OF
EASTERN TEXAS INTO THE LOWER MISSISSIPPI VALLEY...

...Lower Mississippi Valley to the Colorado Front Range...

A powerful upper low over the Four Corners region is the catalyst
for what will be an expansive area of Excessive Rainfall from the
lower elevations of the Central Rockies' Front Range to as far east
as the central Gulf Coast. The tightening pressure gradient between
low pressure in the Southern Plains and a bubble of high pressure
over the Tennessee Valley today is fostering a deep southerly fetch
of Gulf moisture that is wrapping around the northern flank of the
700mb low over northern New Mexico. The ECMWF SAT shows a 300-400
kg/m/s IVT, topping >99th climatological percentile, oriented at
southeast CO and northeast NM. While instability is lacking, the
highly saturated profile when combined with strong synopptic-scale
forcing aloft and upslope enhancement will support a prolong period
of heavy rain below 7,000ft. The Slight Risk remains in place in
these areas, as well as farther east across portions of OK/TX
Panhandles where the pivoting band of >0.75" PWs will result in
efficient rainfall over more saturated soils. Speaking of saturated
soils, much of southern OK and northern TX also remain under the
Slight Risk given their highly saturated soils and any heavy
rainfall rates through the day Tuesday may result in scattered
instances of flash flooding. RAP soundings around OKC show highly
saturated profiles with warm cloud layers up to 10,000ft deep.=20
Some weak instability (<100 J/kg MUCAPE) may be present as well,=20
which while these values are low, they could result in highly=20
efficient rainfall rates with PWs approaching 1.5".=20

Farther south and east, much of eastern TX and the Lower MS Valley
will either be in the warm sector of the storm system or just north
of the surface warm front as it tracks just north of the Gulf
Coast by Tuesday evening. Along the upper coast of Texas, PWs
around 2.0" and warm cloud layers up to 13,000ft deep in some cases
will overlap with MUCAPE that ranges between 500-1000 J/kg. A
highly sheared environment will also support healthy mesocyclones
that can further enhance rainfall rates. The 00Z HREF neighborhood probabilities show low-to-moderate chances (30-50%) for 24-hr
rainfall totals >5" from just nor of I-10 in southeast TX on east
throughout much of southern LA and southern MS. There are actually
some low chance probabilities (10-20%) for isolated totals >8" in
southern LA. Overall, this is a setup that is ripe for flash=20
flooding in the Lower MS Valley with some instances of significant=20
flash flooding in areas where training segments of thunderstorms=20
track over sensitive urbanized environments. Residents should=20
ensure they have a reliable way to receive flash flood warnings=20
from their respective NWS WFOs.

...Northeast...

The upper low responsible for a multi-day stretch of wet weather
throughout the region will begin to make its exit today, but not=20
before it triggers more rounds of heavy rain and thunderstorms. The
ECMWF SAT shows the lingering presence of a >500 kg/m/s southerly IVT
that is responsible for fostering anomalous >90th percentile PWs
above 1.25" in southern New England. Farther west over NY and
eastern PA, the 00Z HREF mean shows anywhere from 500-1,000 J/kg of
MUCAPE available with PWs ranging between 0.75-1.0". Soils have
saturated substantially over the past couple days, resulting in
1-hr FFGs that are <1.00"/hr in the southern tier of NY and
northern PA. Given these factors, the Marginal Risk remains in
place for the potential for additional isolated instances of flash
flooding.=20

...Desert Southwest...

Following a couple days of active weather that has moistened up
soils throughout the region, another round of showers and
thunderstorms is expected today. As mid-level RH values decrease,
the expectation is for more surface-based heating to add to an
increasingly unstable environment aloft (250-500 MUCAPE available
Tuesday afternoon and evening). What is also aiding in the flash=20
flood potential is added synoptic-scale lift as a 500mb low=20
approaches from the north and the diffluent left- exit region of a=20
250mb jet streak moves in overhead. 48-hr QPE estimates as much as
1-2" of rain has fallen in portions of the Marginal Risk area.
Given the sufficient synoptic-scale support is coupled with
increasingly sensitive soils, opted to introduce a Marginal Risk
this forecast cycle for the region today.

Mullinax

Day 2
Valid 12Z Wed May 07 2025 - 12Z Thu May 08 2025

...THERE IS A SLIGHT RISK OF EXCESSIVE RAINFALL OVER PORTIONS OF=20
THE GULF COAST...

By Wednesday, the warm front that lifted through the Upper Texas
coast will stall out along the Gulf Coast and be the focus for
widespread showers and thunderstorms. PWs remain above the 97.5
climatological percentiles from the Upper Texas coast to as far
east as the FL Panhandle. In fact, there are anomalous PWs that
stretch up into northern AL Wednesday afternoon. The flash flood
threat remains greatest along the central Gulf Coast and Lower
MS Valley regions where they are most commonly positioned at the
nose of a >500 kg/m/s IVT and PWs that are topping 1.75" in most
locations. RAP soundings in southern LA Wednesday morning show
low-mid level RH values >90% and warm cloud layers at least=20
11,000ft deep. These soundings also depict tall "skinny CAPE"
profiles with MLCAPE >500 J/kg. Plus, hodographs still suggest the
potential for organized convection given modest mid-level shear and
low-level helicity (sfc-3km >150 m2/s2). The NBM 75th percentile
shows rainfall totals >5" in some cases across the central Gulf
Coast, which is on top of the heavy rainfall that occurred on
Tuesday. The concern would be the SWrly IVT continues to intersect
the stalled frontal boundary in a way that supports training and
back-building convection that produces highly efficient rainfall
rates >2"/hr over soils that are increasingly saturated. No
Moderate Risk was hoisted as of this forecast cycle as there are
still some varying scenarios depicted by model guidance, but should
guidance come into better agreement on a swath of 3-5" amounts
and./or soils grow highly sensitive due to Tuesday's Excessive
Rainfall, a Moderate Risk upgrade could be necessary.=20

The Marginal Risk was expanded north into the hills of northern AL
where FFGs are lower (<2" for 1-hr FFGs) and guidance showed some
modest moisture advection via the aforementioned IVT. Given the
saturated soils in the region and the potential for locally heavy=20
rainfall rates, the Marginal Risk was expanded a little farther=20
north closer ot the TN Valley.

Mullinax

Day 3
Valid 12Z Thu May 08 2025 - 12Z Fri May 09 2025

...THERE IS A MARGINAL RISK OF EXCESSIVE RAINFALL OVER PORTIONS OF
THE GULF COAST...

...Central Gulf Coast...

Thursday and into Thursday night is a near carbon-copy setup to
Wednesday's where the stationary front draped W-E along the Gulf
Coast will continue to act as the initiator in additional
thunderstorms across the South. The central Gulf Coast will remain
the more primed spot for potential flash flooding given the
increasingly sensitive soils in the region after multiple days of
heavy rainfall. PWs ranging between 1.6-1.8" will be common with
MLCAPE that tops 1,000 J/kg. Thunderstorms could produce >2"/hr
rainfall rates across the Marginal Risk area. Should guidance trend
wetter in the coming days, it is possible a Slight Risk upgrade may
be necessary given the soils more sensitive state.=20

...Northeast...

No Marginal Risk was introduced tonight, but this region bears
watching as a cold front approaches from the West. Several guidance
members now show 1-2" of rainfall across portions of the region on
Thursday, however they vary on where those heavier amounts are most
likely to occur. A positively tilted upper trough approaching from
Ontario will provide plenty of upper-level ascent while the=20
approaching cold front acts as the surface/low-level trigger for=20
initiating thunderstorms. Plus, some guidance members show the=20 positively-tilted trough cutting off just enough to where an 850mb=20
low forms near the Northeast coast. This is not the case across all
guidance and is resulting in rainfall swaths that are farther=20
north over the interior Northeast (GFS/ECMWF/ICON), or as far=20
south and east as the I-95 corridor (EC-AIFS/CMC/UKMET/RRFS). With
lingering uncertainty in the forecast, the Marginal Risk upgrade=20
was held off this forecast cycle. But given the highly saturated=20
soils in the region, it is possible a Marginal Risk will be=20
necessary in future forecast updates once confidence increases in=20
where the heaviest swath of rainfall occurs.=20


Mullinax


Day 1 threat area: https://urldefense.com/v3/__https://www.wpc.ncep.noaa.go= v/qpf/94epoints.txt__;!!DZ3fjg!9fQEh6MjNh71b0WOto8EKhkTx2eifX4xmGzX2Whll6eE= DeQ_vpwGBlphGafmXExNLFn7jY9W_N4ihEOfdkeUTqpEVHY$=20
Day 2 threat area: https://urldefense.com/v3/__https://www.wpc.ncep.noaa.go= v/qpf/98epoints.txt__;!!DZ3fjg!9fQEh6MjNh71b0WOto8EKhkTx2eifX4xmGzX2Whll6eE= DeQ_vpwGBlphGafmXExNLFn7jY9W_N4ihEOfdkeU6VahyM8$=20
Day 3 threat area: https://urldefense.com/v3/__https://www.wpc.ncep.noaa.go= v/qpf/99epoints.txt__;!!DZ3fjg!9fQEh6MjNh71b0WOto8EKhkTx2eifX4xmGzX2Whll6eE= DeQ_vpwGBlphGafmXExNLFn7jY9W_N4ihEOfdkeU5EU4uTA$=20

=3D =3D =3D
To unsubscribe from WX-STORM and you already have a login, go to https://lists.illinois.edu and use the "Unsubscribe" link. Otherwise email Chris Novy at cnovy@cox.net and ask to be removed from WX-STORM.

--- SBBSecho 3.20-Linux
* Origin: capitolcityonline.net * Telnet/SSH:2022/HTTP (1:2320/105)

FOUS30 KWBC 061551
QPFERD

Excessive Rainfall Discussion
NWS Weather Prediction Center College Park MD
1151 AM EDT Tue May 6 2025

Day 1
Valid 16Z Tue May 06 2025 - 12Z Wed May 07 2025

...THERE IS A MODERATE RISK OF EXCESSIVE RAINFALL OVER PORTIONS OF
EASTERN TEXAS INTO THE LOWER MISSISSIPPI VALLEY...

...16Z Update...

The Moderate Risk area was trimmed a bit on the northwestern side
with some of the latest CAMs guidance indicating that there will be
less coverage of convection in between the main MCS to the south
and east centered over northern Louisiana, and the upslope focused
precip (with help from an upper level shortwave) to the west from
the TX/OK Panhandles northwest into southern CO. THe Slight Risk
area was expanded to the north and west to include a portion of the
I-25 corridor near Colorado Springs, and the surrounding Marginal
was expanded well north along I-25 to include Denver and Ft.
Collins, with more rainfall the further south you go. This is due
in part to rainfall amounts being quite abnormal for this area, and
while associated flash flooding should be isolated given dry
antecedent soil conditions and heavy snow in the higher elevations
of the Front Range, the urban factor should support isolated
instances through the night. For CO in general this will be a
long-duration stratiform rain event in an area that doesn't have
too many of those in a given year, so the abnormality of it could
overwhelm flood-prone areas.

Around the DFW Metroplex, a line of intense thunderstorms is moving
across the metros right now. Once the line clears to the east, that
should be the end of the flooding threat for the day. For points
south and west of there, the Slight and Marginal Risk areas were
trimmed accordingly.

The biggest change with this update was to introduce a Slight Risk
upgrade for Central New York and portions of the Southern Tier
south into northeastern Pennsylvania, in coordination with
BGM/Binghamton, NY and BUF/Buffalo, NY forecast offices. Similar to
yesterday in the DMV, albeit further north, the same upper level=20
low is expected to produce additional areas of training convection
from around the Mason-Dixon line north into NY. For the Slight Risk
area, additional upper level energy will allow for greater
organization as compared with areas further south, and despite the
fast movement of individual cells, the focus of the heaviest rains
over areas that have seen multiple afternoons of heavy rainfall
prior to this event have left the soils very saturated and
therefore unable to absorb much additional rainfall. The
surrounding Marginal was expanded back into MD, Northern VA, and
the eastern panhandle of WV with this update, as convection is
already beginning to break out in these areas. Again, it's unlikely
the storms will be nearly as organized today around and south of
the Mason-Dixon line as compared with yesterday, so a Marginal
should be all that is needed.

The Marginal risk out west in southern NV, far eastern CA, and
western AZ remains unchanged with this update as widely scattered
convection is expected once again today, and at last much of
southern NV and northwestern AZ have very saturated soils from
yesterday's convection, favoring the redevelopment of additional
flash flooding in this area with today's forecast storms.

Wegman

...Previous Discussion...

...Lower Mississippi Valley to the Colorado Front Range...

A powerful upper low over the Four Corners region is the catalyst
for what will be an expansive area of Excessive Rainfall from the
lower elevations of the Central Rockies' Front Range to as far east
as the central Gulf Coast. The tightening pressure gradient between
low pressure in the Southern Plains and a bubble of high pressure
over the Tennessee Valley today is fostering a deep southerly fetch
of Gulf moisture that is wrapping around the northern flank of the
700mb low over northern New Mexico. The ECMWF SAT shows a 300-400
kg/m/s IVT, topping >99th climatological percentile, oriented at
southeast CO and northeast NM. While instability is lacking, the
highly saturated profile when combined with strong synopptic-scale
forcing aloft and upslope enhancement will support a prolong period
of heavy rain below 7,000ft. The Slight Risk remains in place in
these areas, as well as farther east across portions of OK/TX
Panhandles where the pivoting band of >0.75" PWs will result in
efficient rainfall over more saturated soils. Speaking of saturated
soils, much of southern OK and northern TX also remain under the
Slight Risk given their highly saturated soils and any heavy
rainfall rates through the day Tuesday may result in scattered
instances of flash flooding. RAP soundings around OKC show highly
saturated profiles with warm cloud layers up to 10,000ft deep.
Some weak instability (<100 J/kg MUCAPE) may be present as well,
which while these values are low, they could result in highly
efficient rainfall rates with PWs approaching 1.5".

Farther south and east, much of eastern TX and the Lower MS Valley
will either be in the warm sector of the storm system or just north
of the surface warm front as it tracks just north of the Gulf
Coast by Tuesday evening. Along the upper coast of Texas, PWs
around 2.0" and warm cloud layers up to 13,000ft deep in some cases
will overlap with MUCAPE that ranges between 500-1000 J/kg. A
highly sheared environment will also support healthy mesocyclones
that can further enhance rainfall rates. The 00Z HREF neighborhood probabilities show low-to-moderate chances (30-50%) for 24-hr
rainfall totals >5" from just nor of I-10 in southeast TX on east
throughout much of southern LA and southern MS. There are actually
some low chance probabilities (10-20%) for isolated totals >8" in
southern LA. Overall, this is a setup that is ripe for flash
flooding in the Lower MS Valley with some instances of significant
flash flooding in areas where training segments of thunderstorms
track over sensitive urbanized environments. Residents should
ensure they have a reliable way to receive flash flood warnings
from their respective NWS WFOs.

...Northeast...

The upper low responsible for a multi-day stretch of wet weather
throughout the region will begin to make its exit today, but not
before it triggers more rounds of heavy rain and thunderstorms. The
ECMWF SAT shows the lingering presence of a >500 kg/m/s southerly IVT
that is responsible for fostering anomalous >90th percentile PWs
above 1.25" in southern New England. Farther west over NY and
eastern PA, the 00Z HREF mean shows anywhere from 500-1,000 J/kg of
MUCAPE available with PWs ranging between 0.75-1.0". Soils have
saturated substantially over the past couple days, resulting in
1-hr FFGs that are <1.00"/hr in the southern tier of NY and
northern PA. Given these factors, the Marginal Risk remains in
place for the potential for additional isolated instances of flash
flooding.

...Desert Southwest...

Following a couple days of active weather that has moistened up
soils throughout the region, another round of showers and
thunderstorms is expected today. As mid-level RH values decrease,
the expectation is for more surface-based heating to add to an
increasingly unstable environment aloft (250-500 MUCAPE available
Tuesday afternoon and evening). What is also aiding in the flash
flood potential is added synoptic-scale lift as a 500mb low
approaches from the north and the diffluent left- exit region of a
250mb jet streak moves in overhead. 48-hr QPE estimates as much as
1-2" of rain has fallen in portions of the Marginal Risk area.
Given the sufficient synoptic-scale support is coupled with
increasingly sensitive soils, opted to introduce a Marginal Risk
this forecast cycle for the region today.

Mullinax

Day 2
Valid 12Z Wed May 07 2025 - 12Z Thu May 08 2025

...THERE IS A SLIGHT RISK OF EXCESSIVE RAINFALL OVER PORTIONS OF
THE GULF COAST...

By Wednesday, the warm front that lifted through the Upper Texas
coast will stall out along the Gulf Coast and be the focus for
widespread showers and thunderstorms. PWs remain above the 97.5
climatological percentiles from the Upper Texas coast to as far
east as the FL Panhandle. In fact, there are anomalous PWs that
stretch up into northern AL Wednesday afternoon. The flash flood
threat remains greatest along the central Gulf Coast and Lower
MS Valley regions where they are most commonly positioned at the
nose of a >500 kg/m/s IVT and PWs that are topping 1.75" in most
locations. RAP soundings in southern LA Wednesday morning show
low-mid level RH values >90% and warm cloud layers at least
11,000ft deep. These soundings also depict tall "skinny CAPE"
profiles with MLCAPE >500 J/kg. Plus, hodographs still suggest the
potential for organized convection given modest mid-level shear and
low-level helicity (sfc-3km >150 m2/s2). The NBM 75th percentile
shows rainfall totals >5" in some cases across the central Gulf
Coast, which is on top of the heavy rainfall that occurred on
Tuesday. The concern would be the SWrly IVT continues to intersect
the stalled frontal boundary in a way that supports training and
back-building convection that produces highly efficient rainfall
rates >2"/hr over soils that are increasingly saturated. No
Moderate Risk was hoisted as of this forecast cycle as there are
still some varying scenarios depicted by model guidance, but should
guidance come into better agreement on a swath of 3-5" amounts
and./or soils grow highly sensitive due to Tuesday's Excessive
Rainfall, a Moderate Risk upgrade could be necessary.

The Marginal Risk was expanded north into the hills of northern AL
where FFGs are lower (<2" for 1-hr FFGs) and guidance showed some
modest moisture advection via the aforementioned IVT. Given the
saturated soils in the region and the potential for locally heavy
rainfall rates, the Marginal Risk was expanded a little farther
north closer ot the TN Valley.

Mullinax

Day 3
Valid 12Z Thu May 08 2025 - 12Z Fri May 09 2025

...THERE IS A MARGINAL RISK OF EXCESSIVE RAINFALL OVER PORTIONS OF
THE GULF COAST...

...Central Gulf Coast...

Thursday and into Thursday night is a near carbon-copy setup to
Wednesday's where the stationary front draped W-E along the Gulf
Coast will continue to act as the initiator in additional
thunderstorms across the South. The central Gulf Coast will remain
the more primed spot for potential flash flooding given the
increasingly sensitive soils in the region after multiple days of
heavy rainfall. PWs ranging between 1.6-1.8" will be common with
MLCAPE that tops 1,000 J/kg. Thunderstorms could produce >2"/hr
rainfall rates across the Marginal Risk area. Should guidance trend
wetter in the coming days, it is possible a Slight Risk upgrade may
be necessary given the soils more sensitive state.

...Northeast...

No Marginal Risk was introduced tonight, but this region bears
watching as a cold front approaches from the West. Several guidance
members now show 1-2" of rainfall across portions of the region on
Thursday, however they vary on where those heavier amounts are most
likely to occur. A positively tilted upper trough approaching from
Ontario will provide plenty of upper-level ascent while the
approaching cold front acts as the surface/low-level trigger for
initiating thunderstorms. Plus, some guidance members show the positively-tilted trough cutting off just enough to where an 850mb
low forms near the Northeast coast. This is not the case across all
guidance and is resulting in rainfall swaths that are farther
north over the interior Northeast (GFS/ECMWF/ICON), or as far
south and east as the I-95 corridor (EC-AIFS/CMC/UKMET/RRFS). With
lingering uncertainty in the forecast, the Marginal Risk upgrade
was held off this forecast cycle. But given the highly saturated
soils in the region, it is possible a Marginal Risk will be
necessary in future forecast updates once confidence increases in
where the heaviest swath of rainfall occurs.


Mullinax


Day 1 threat area: https://urldefense.com/v3/__https://www.wpc.ncep.noaa.go= v/qpf/94epoints.txt__;!!DZ3fjg!8YGEMNH7anaq1fMdyhZrKvBDHOfcToj2iLIDx0U6Tfwp= bJ3JjgfBkFOhj2lrRZNzqED76974CZuH_y1bgMk3EP5Pc84$=20
Day 2 threat area: https://urldefense.com/v3/__https://www.wpc.ncep.noaa.go= v/qpf/98epoints.txt__;!!DZ3fjg!8YGEMNH7anaq1fMdyhZrKvBDHOfcToj2iLIDx0U6Tfwp= bJ3JjgfBkFOhj2lrRZNzqED76974CZuH_y1bgMk3IGHMjdE$=20
Day 3 threat area: https://urldefense.com/v3/__https://www.wpc.ncep.noaa.go= v/qpf/99epoints.txt__;!!DZ3fjg!8YGEMNH7anaq1fMdyhZrKvBDHOfcToj2iLIDx0U6Tfwp= bJ3JjgfBkFOhj2lrRZNzqED76974CZuH_y1bgMk3zClE4Wk$=20

=3D =3D =3D
To unsubscribe from WX-STORM and you already have a login, go to https://lists.illinois.edu and use the "Unsubscribe" link. Otherwise email Chris Novy at cnovy@cox.net and ask to be removed from WX-STORM.

--- SBBSecho 3.20-Linux
* Origin: capitolcityonline.net * Telnet/SSH:2022/HTTP (1:2320/105)

FOUS30 KWBC 062015
QPFERD

Excessive Rainfall Discussion
NWS Weather Prediction Center College Park MD
415 PM EDT Tue May 6 2025

Day 1
Valid 16Z Tue May 06 2025 - 12Z Wed May 07 2025

...THERE IS A MODERATE RISK OF EXCESSIVE RAINFALL OVER PORTIONS OF
EASTERN TEXAS INTO THE LOWER MISSISSIPPI VALLEY...

...16Z Update...

The Moderate Risk area was trimmed a bit on the northwestern side
with some of the latest CAMs guidance indicating that there will be
less coverage of convection in between the main MCS to the south
and east centered over northern Louisiana, and the upslope focused
precip (with help from an upper level shortwave) to the west from
the TX/OK Panhandles northwest into southern CO. THe Slight Risk
area was expanded to the north and west to include a portion of the
I-25 corridor near Colorado Springs, and the surrounding Marginal
was expanded well north along I-25 to include Denver and Ft.
Collins, with more rainfall the further south you go. This is due
in part to rainfall amounts being quite abnormal for this area, and
while associated flash flooding should be isolated given dry
antecedent soil conditions and heavy snow in the higher elevations
of the Front Range, the urban factor should support isolated
instances through the night. For CO in general this will be a
long-duration stratiform rain event in an area that doesn't have
too many of those in a given year, so the abnormality of it could
overwhelm flood-prone areas.

Around the DFW Metroplex, a line of intense thunderstorms is moving
across the metros right now. Once the line clears to the east, that
should be the end of the flooding threat for the day. For points
south and west of there, the Slight and Marginal Risk areas were
trimmed accordingly.

The biggest change with this update was to introduce a Slight Risk
upgrade for Central New York and portions of the Southern Tier
south into northeastern Pennsylvania, in coordination with
BGM/Binghamton, NY and BUF/Buffalo, NY forecast offices. Similar to
yesterday in the DMV, albeit further north, the same upper level
low is expected to produce additional areas of training convection
from around the Mason-Dixon line north into NY. For the Slight Risk
area, additional upper level energy will allow for greater
organization as compared with areas further south, and despite the
fast movement of individual cells, the focus of the heaviest rains
over areas that have seen multiple afternoons of heavy rainfall
prior to this event have left the soils very saturated and
therefore unable to absorb much additional rainfall. The
surrounding Marginal was expanded back into MD, Northern VA, and
the eastern panhandle of WV with this update, as convection is
already beginning to break out in these areas. Again, it's unlikely
the storms will be nearly as organized today around and south of
the Mason-Dixon line as compared with yesterday, so a Marginal
should be all that is needed.

The Marginal risk out west in southern NV, far eastern CA, and
western AZ remains unchanged with this update as widely scattered
convection is expected once again today, and at last much of
southern NV and northwestern AZ have very saturated soils from
yesterday's convection, favoring the redevelopment of additional
flash flooding in this area with today's forecast storms.

Wegman

...Previous Discussion...

...Lower Mississippi Valley to the Colorado Front Range...

A powerful upper low over the Four Corners region is the catalyst
for what will be an expansive area of Excessive Rainfall from the
lower elevations of the Central Rockies' Front Range to as far east
as the central Gulf Coast. The tightening pressure gradient between
low pressure in the Southern Plains and a bubble of high pressure
over the Tennessee Valley today is fostering a deep southerly fetch
of Gulf moisture that is wrapping around the northern flank of the
700mb low over northern New Mexico. The ECMWF SAT shows a 300-400
kg/m/s IVT, topping >99th climatological percentile, oriented at
southeast CO and northeast NM. While instability is lacking, the
highly saturated profile when combined with strong synopptic-scale
forcing aloft and upslope enhancement will support a prolong period
of heavy rain below 7,000ft. The Slight Risk remains in place in
these areas, as well as farther east across portions of OK/TX
Panhandles where the pivoting band of >0.75" PWs will result in
efficient rainfall over more saturated soils. Speaking of saturated
soils, much of southern OK and northern TX also remain under the
Slight Risk given their highly saturated soils and any heavy
rainfall rates through the day Tuesday may result in scattered
instances of flash flooding. RAP soundings around OKC show highly
saturated profiles with warm cloud layers up to 10,000ft deep.
Some weak instability (<100 J/kg MUCAPE) may be present as well,
which while these values are low, they could result in highly
efficient rainfall rates with PWs approaching 1.5".

Farther south and east, much of eastern TX and the Lower MS Valley
will either be in the warm sector of the storm system or just north
of the surface warm front as it tracks just north of the Gulf
Coast by Tuesday evening. Along the upper coast of Texas, PWs
around 2.0" and warm cloud layers up to 13,000ft deep in some cases
will overlap with MUCAPE that ranges between 500-1000 J/kg. A
highly sheared environment will also support healthy mesocyclones
that can further enhance rainfall rates. The 00Z HREF neighborhood probabilities show low-to-moderate chances (30-50%) for 24-hr
rainfall totals >5" from just nor of I-10 in southeast TX on east
throughout much of southern LA and southern MS. There are actually
some low chance probabilities (10-20%) for isolated totals >8" in
southern LA. Overall, this is a setup that is ripe for flash
flooding in the Lower MS Valley with some instances of significant
flash flooding in areas where training segments of thunderstorms
track over sensitive urbanized environments. Residents should
ensure they have a reliable way to receive flash flood warnings
from their respective NWS WFOs.

...Northeast...

The upper low responsible for a multi-day stretch of wet weather
throughout the region will begin to make its exit today, but not
before it triggers more rounds of heavy rain and thunderstorms. The
ECMWF SAT shows the lingering presence of a >500 kg/m/s southerly IVT
that is responsible for fostering anomalous >90th percentile PWs
above 1.25" in southern New England. Farther west over NY and
eastern PA, the 00Z HREF mean shows anywhere from 500-1,000 J/kg of
MUCAPE available with PWs ranging between 0.75-1.0". Soils have
saturated substantially over the past couple days, resulting in
1-hr FFGs that are <1.00"/hr in the southern tier of NY and
northern PA. Given these factors, the Marginal Risk remains in
place for the potential for additional isolated instances of flash
flooding.

...Desert Southwest...

Following a couple days of active weather that has moistened up
soils throughout the region, another round of showers and
thunderstorms is expected today. As mid-level RH values decrease,
the expectation is for more surface-based heating to add to an
increasingly unstable environment aloft (250-500 MUCAPE available
Tuesday afternoon and evening). What is also aiding in the flash
flood potential is added synoptic-scale lift as a 500mb low
approaches from the north and the diffluent left- exit region of a
250mb jet streak moves in overhead. 48-hr QPE estimates as much as
1-2" of rain has fallen in portions of the Marginal Risk area.
Given the sufficient synoptic-scale support is coupled with
increasingly sensitive soils, opted to introduce a Marginal Risk
this forecast cycle for the region today.

Mullinax

Day 2
Valid 12Z Wed May 07 2025 - 12Z Thu May 08 2025

...THERE IS A MODERATE RISK OF EXCESSIVE RAINFALL FOR PORTIONS OF
SOUTHEASTERN LOUISIANA...

...2030Z Update...

...Gulf Coast...

In coordination with LIX/Slidell, LA forecast office, a Moderate
Risk upgrade was introduced with this update for portions of
southeastern Louisiana, including the Baton Rouge and New Orleans
metros. Strong thunderstorms producing very heavy rainfall with
maximum rates up to 3 inches per hour are expected to be ongoing
across the Moderate Risk region at the start of the period 12Z
Wednesday morning. The expectation is that heavy rain will be
ongoing in the few hours prior to the start of the period, such
that additional rainfall about midway through this heavy rainfall
event at 12Z will significantly worsen already ongoing flooding.
Thus, many of the flooding impacts from the Day 1 Moderate Risk=20
will be experienced into the first part of this Day 2 time frame.

It is very important to note that there has been a notable
southward trend in the guidance regarding where the axis of
heaviest rainfall will set up, with the I-10 corridor from Baton
Rouge through New Orleans the likely northernmost extent of the
multiple inches of rain forecast for this area. Thus, any
additional southward trend would require a notable downgrade in the
forecasted risk areas. In other words, the "bust potential" of this
event has notably increased. Nonetheless, given the susceptibility
of the Moderate Risk area to flash flooding in both aforementioned
urban centers and along the Atchafalaya River and its spillways,
the current forecasted rainfall during this period, though almost
entirely Wednesday morning, would still likely cause numerous
instances of flash flooding, some of whom may be significant.

Regardless of exactly where the heaviest storms are occurring at
the start of the period Wednesday morning, there is very good
consensus that by as early as late Wednesday morning, the storms
will have all pushed south into the Gulf, leaving much of the
Louisiana coast in much lighter outflow from those storms to the
north of their cores. Thus, most of the threat is prior to 18Z,
with very likely downgrades likely thereafter.

Further to the west, the Slight Risk area was expanded west to=20
include the Houston metro in coordination with HGX/Houston, TX=20
forecast office. The aforementioned southward trend in the=20
guidance is notable here as well, but there appears to be better=20
consensus there may be newly developed afternoon convection
impacting the Houston Metro Wednesday afternoon. Urbanization and susceptibility to flash flooding of that area was a considerable
factor in the upgrade for this area.

...Mid-South...

An expansive Marginal Risk area was added with this update from
Kansas to north Georgia ahead of a dying upper level low that will
slowly track eastward across the region, providing enough forcing
for widely scattered thunderstorms to take advantage of still
considerable Gulf moisture in the area. Much of this area has been
hit recently with heavy rains, which will locally increase the
flash flooding risk, especially if the upper low can help organize
any of the convection.

...Florida Space Coast...

A small Marginal Risk was added to the ERO for urbanized portions
of the I-95 corridor through north Florida along the Space Coast. A
stalled out cold front is likely to provide enough forcing given
the plentiful moisture around (PWATs exceeding 1.75 inches) to
allow any storms that form, perhaps along the sea breeze or along
the cold pools of other storms, to be slow moving and have enough
moisture to locally cause heavy rains. Isolated instances of flash
flooding are possible.

Wegman

...Previous Discussion...

By Wednesday, the warm front that lifted through the Upper Texas
coast will stall out along the Gulf Coast and be the focus for
widespread showers and thunderstorms. PWs remain above the 97.5
climatological percentiles from the Upper Texas coast to as far
east as the FL Panhandle. In fact, there are anomalous PWs that
stretch up into northern AL Wednesday afternoon. The flash flood
threat remains greatest along the central Gulf Coast and Lower
MS Valley regions where they are most commonly positioned at the
nose of a >500 kg/m/s IVT and PWs that are topping 1.75" in most
locations. RAP soundings in southern LA Wednesday morning show
low-mid level RH values >90% and warm cloud layers at least
11,000ft deep. These soundings also depict tall "skinny CAPE"
profiles with MLCAPE >500 J/kg. Plus, hodographs still suggest the
potential for organized convection given modest mid-level shear and
low-level helicity (sfc-3km >150 m2/s2). The NBM 75th percentile
shows rainfall totals >5" in some cases across the central Gulf
Coast, which is on top of the heavy rainfall that occurred on
Tuesday. The concern would be the SWrly IVT continues to intersect
the stalled frontal boundary in a way that supports training and
back-building convection that produces highly efficient rainfall
rates >2"/hr over soils that are increasingly saturated. No
Moderate Risk was hoisted as of this forecast cycle as there are
still some varying scenarios depicted by model guidance, but should
guidance come into better agreement on a swath of 3-5" amounts
and./or soils grow highly sensitive due to Tuesday's Excessive
Rainfall, a Moderate Risk upgrade could be necessary.

The Marginal Risk was expanded north into the hills of northern AL
where FFGs are lower (<2" for 1-hr FFGs) and guidance showed some
modest moisture advection via the aforementioned IVT. Given the
saturated soils in the region and the potential for locally heavy
rainfall rates, the Marginal Risk was expanded a little farther
north closer ot the TN Valley.

Mullinax

Day 3
Valid 12Z Thu May 08 2025 - 12Z Fri May 09 2025

...THERE IS A SLIGHT RISK OF EXCESSIVE RAINFALL OVER PORTIONS OF=20
THE CENTRAL GULF COAST...

...2030Z Update...

...Central Gulf Coast...

In coordination with LIX/Slidell, LA forecast office, a Slight Risk
upgrade was introduced with this update for portions of the central
Gulf Coast. The stalled front over the area will continue to
provide the forcing needed for additional convection to form along
the coast, possibly intruding inland as far north as New Orleans.
The area is expected to be very susceptible to flash flooding from
additional rainfall after today's and Wednesday's storms, but it's
very possible that the strongest storms impacting the area remain
offshore enough to not pose as high a flash flooding risk. However,
despite this uncertainty with where the storms will form countered
with the certainty that the soils and rivers will be full from
prior days' rainfall, there's enough certainty for the risk
upgrade.=20

...Southeast...

The Marginal Risk was expanded along Florida's First and Space
Coasts as well as northwest into Arkansas with this update. A
longwave very positively tilted trough will continue to provide the
forcing needed for another day of convective development across the
Southeast as plentiful Gulf moisture remains south of the surface
cold front. Due to the diffuse nature of the front and low
predictability of any surface fronts and cold pools, expect the
storms to be mostly disorganized and widely scattered, which favors
the Marginal Risk mostly for areas where the soils are more
saturated due to prior rains. For Florida, the same front will be
stuck along the coast as the Day 2/Wednesday period, resulting in
the potential for similar convection again in this period Thursday afternoon.=20

...Deep South Texas...

A broad Marginal was added with this update on the tail end of the
front over the western Gulf and into Texas. A significant cold
front pushing south out of central Texas will meet up with deep
Gulf moisture over the western Gulf, which will allow for scattered
storms across the area, which will force additional convection from
prior storms' cold pools. This most areas will see at least some
period of heavy rain, which will be capable of causing isolated
instances of flash flooding.

...Northeast...

A very potent digging shortwave trough will move due south down the Appalachians on Thursday. It will tap into increasing Gulf/Atlantic
moisture downwind of the Gulf convection, drawing moisture and
instability northward and into the Northeast, with the shortwave
providing the forcing. Instability will be the limiting factor for
any storms, with the initial development of those storms perhaps
having the greatest flash flooding threat. By the overnight
Thursday night, expect a broad swath of moderate rainfall with
embedded convection tracking northward into the Northeast. Once
again some of these same areas have had or are having heavy rain
impact the area the past couple days through the Day 2 period, so
isolated instance of flash flooding in this area appear likely with
the additional rainfall.

Wegman

...Previous Discussion...

...Central Gulf Coast...

Thursday and into Thursday night is a near carbon-copy setup to
Wednesday's where the stationary front draped W-E along the Gulf
Coast will continue to act as the initiator in additional
thunderstorms across the South. The central Gulf Coast will remain
the more primed spot for potential flash flooding given the
increasingly sensitive soils in the region after multiple days of
heavy rainfall. PWs ranging between 1.6-1.8" will be common with
MLCAPE that tops 1,000 J/kg. Thunderstorms could produce >2"/hr
rainfall rates across the Marginal Risk area. Should guidance trend
wetter in the coming days, it is possible a Slight Risk upgrade may
be necessary given the soils more sensitive state.

...Northeast...

No Marginal Risk was introduced tonight, but this region bears
watching as a cold front approaches from the West. Several guidance
members now show 1-2" of rainfall across portions of the region on
Thursday, however they vary on where those heavier amounts are most
likely to occur. A positively tilted upper trough approaching from
Ontario will provide plenty of upper-level ascent while the
approaching cold front acts as the surface/low-level trigger for
initiating thunderstorms. Plus, some guidance members show the positively-tilted trough cutting off just enough to where an 850mb
low forms near the Northeast coast. This is not the case across all
guidance and is resulting in rainfall swaths that are farther
north over the interior Northeast (GFS/ECMWF/ICON), or as far
south and east as the I-95 corridor (EC-AIFS/CMC/UKMET/RRFS). With
lingering uncertainty in the forecast, the Marginal Risk upgrade
was held off this forecast cycle. But given the highly saturated
soils in the region, it is possible a Marginal Risk will be
necessary in future forecast updates once confidence increases in
where the heaviest swath of rainfall occurs.


Mullinax


Day 1 threat area: https://urldefense.com/v3/__https://www.wpc.ncep.noaa.go= v/qpf/94epoints.txt__;!!DZ3fjg!5ZF9hQ-4ZSoIiepNqGlLm8NzG8Fm-qMbRrRlOFoe7LWG= SEeEKJGFA9JTJBRPACznkKdbq7DUkc9OLwIyTpknABVmP7s$=20
Day 2 threat area: https://urldefense.com/v3/__https://www.wpc.ncep.noaa.go= v/qpf/98epoints.txt__;!!DZ3fjg!5ZF9hQ-4ZSoIiepNqGlLm8NzG8Fm-qMbRrRlOFoe7LWG= SEeEKJGFA9JTJBRPACznkKdbq7DUkc9OLwIyTpknUZ8FPak$=20
Day 3 threat area: https://urldefense.com/v3/__https://www.wpc.ncep.noaa.go= v/qpf/99epoints.txt__;!!DZ3fjg!5ZF9hQ-4ZSoIiepNqGlLm8NzG8Fm-qMbRrRlOFoe7LWG= SEeEKJGFA9JTJBRPACznkKdbq7DUkc9OLwIyTpknarvmZNs$=20

=3D =3D =3D
To unsubscribe from WX-STORM and you already have a login, go to https://lists.illinois.edu and use the "Unsubscribe" link. Otherwise email Chris Novy at cnovy@cox.net and ask to be removed from WX-STORM.

--- SBBSecho 3.20-Linux
* Origin: capitolcityonline.net * Telnet/SSH:2022/HTTP (1:2320/105)

FOUS30 KWBC 070043
QPFERD

Excessive Rainfall Discussion
NWS Weather Prediction Center College Park MD
843 PM EDT Tue May 6 2025

Day 1
Valid 01Z Wed May 07 2025 - 12Z Wed May 07 2025

...THERE IS A MODERATE RISK OF EXCESSIVE RAINFALL OVER PORTIONS OF
EASTERN TEXAS INTO THE LOWER MISSISSIPPI VALLEY...

...East Texas into Lower Mississippi Valley...

Steady progression of heavy convection will continue through the
evening with a combination of discrete cells co-located within a
broad MCS propagation along the northern periphery of a sharp
theta_E gradient aligned with a slow-moving warm front. Rainfall
rates this evening will settle between 1-3"/hr with a few cells
over Southern LA and MS potentially breaching 3"/hr, especially
during intra-hour tendencies. Ascent pattern remains very favorable
with a broad cyclonic ULL positioned over the Southern Plains with
extension back into the Western CONUS. HREF EAS prob fields for >3"
is very high (>50%) across all of Central LA extending east into
the mouth of the MS just north of New Orleans. This places some
formidable metro populations within an expected corridor of heavy
rainfall that will likely lead to flash flooding through the
overnight hours. There's already been several flood reports with
associated flash flood warnings lined up along I-20 across the
ArkLaTex, now expanding east through Northern LA. Expect that trend
to continue into MS with the Jackson metro next in line for
anticipated impacts. Despite some lower EAS probs for >3" within
Jackson, there's been a considerable jump in the recent HRRR output
with a solid 2-4" anticipated within the zone of impact from the
propagating MCS. With the cell mergers taking place already across
Southwest LA, there will be a considerable footprint of 2+" totals
with embedded 3-5" amounts that will allow for broad areal coverage
of flash flood warnings the next several hours. The previously
inherited MDT risk from the afternoon remains for many, although
some of the risk was trimmed due to convective impacts already
occurring earlier in the afternoon and evening.=20

A line of convection remains situated across portions of East TX as
well thanks to parallel boundary layer flow up against a slow
moving cold front that appears to be quickly losing steam as it
moves eastward. Countering LLJ is causing significant degradation
of the frontal progression, something that will allow for training
echoes to be a common occurrence over the course of the evening.=20
The next few hours will be the most concerning periods before the=20
setup slowly shifts east into the Lower Sabine allowing for an=20
addition few inches to potentially fall over the southern portion=20
of I-45. The Houston metro will be an area of interest this evening
as the slow storm motions could lead to some locally enhanced=20
totals within the urban corridor. The best threat still looks to=20
lie northeast of there, but the metro remains solidly in the SLGT=20
risk for the update.=20

A MRGL risk now encompasses Deep South TX as hourly hi-res depicts
a stronger mid-level perturbation ejecting out of Coahuila with=20
scattered thunderstorm development likely overnight, blossoming to=20
the east as it interacts with the western fringes of the LLJ=20
component. Areas outside the urban zones will be tough to flood=20
considering the setup, but there are some indications of locally=20
heavy totals >2" in spots, so decided to expand further south to=20
cover for the low-end threat.=20

...Great Basin...

Slow-moving ULL situated over the Colorado River Basin along with
primary diurnal destabilization has led to scattered heavy
thunderstorms to blossom across portions of Southern NV, Southeast
CA, and now moving into Western AZ. This setup is a mid-tier MRGL
risk with a majority of the rainfall being beneficial for the area,
but sufficient low to mid-level buoyancy coupled with favorable
upper forcing and steep lapse rates could yield a few lingering
storms to exceed 0.50"/hr rates capable of flash flood concerns the
next 2-4 hours. Once we have a sufficient diurnal heat loss after
sunset, the convective setup will dwindle with any activity
petering out to just light showers overnight.=20

...Central and Southern Plains...

The primary ULL across the Plains will allow for a continued
elevated convective threat with a few heavier cores located under,
and just north of the closed reflection. Regional theta_E's are not
very impressive at the moment, but as noted via regional radar
output, some stronger mid-level vorticity is pivoting around the
general circulation allowing for some heavier convective cores to
initiate over the TX Panhandle and Southwest KS. The main precip
shield will undergo a relatively solid west to east axis of steady precipitation with a mature axis of deformation on the northwest
flank of the ULL center. This will lead to 1-2" totals, locally
higher to occur over portions of Southwest and South-Central KS
down along the OK state line. The threat for flash flooding is low,
but still within the lower threshold when assessing the cumulative
nature of the precip anticipated. A MRGL risk was maintained for
the above area.

...Northeast...

Remnant ULL situated over the interior Northeast U.S. will pinwheel
northward with shower and storm activity continuing over the next
few hours within the Catskills and western flank of the Hudson
Valley. Elevated convective clusters will linger under the primary
circulation, but will begin to falter as we move into the overnight
period as drier air gets pulled northward around the circulation.
Additional totals of 1" are plausible across places east and
southeast of Lake Ontario which could offer an isolated flash flood
threat for areas that have already seen decent rainfall this
afternoon. The areas that had the greatest impacts earlier will
likely see the threat wane in the next hour as they see the dry air
advection regime take place.=20

Kleebauer


Day 2
Valid 12Z Wed May 07 2025 - 12Z Thu May 08 2025

...THERE IS A MODERATE RISK OF EXCESSIVE RAINFALL FOR PORTIONS OF
SOUTHEASTERN LOUISIANA...

...2030Z Update...

...Gulf Coast...

In coordination with LIX/Slidell, LA forecast office, a Moderate
Risk upgrade was introduced with this update for portions of
southeastern Louisiana, including the Baton Rouge and New Orleans
metros. Strong thunderstorms producing very heavy rainfall with
maximum rates up to 3 inches per hour are expected to be ongoing
across the Moderate Risk region at the start of the period 12Z
Wednesday morning. The expectation is that heavy rain will be
ongoing in the few hours prior to the start of the period, such
that additional rainfall about midway through this heavy rainfall
event at 12Z will significantly worsen already ongoing flooding.
Thus, many of the flooding impacts from the Day 1 Moderate Risk
will be experienced into the first part of this Day 2 time frame.

It is very important to note that there has been a notable
southward trend in the guidance regarding where the axis of
heaviest rainfall will set up, with the I-10 corridor from Baton
Rouge through New Orleans the likely northernmost extent of the
multiple inches of rain forecast for this area. Thus, any
additional southward trend would require a notable downgrade in the
forecasted risk areas. In other words, the "bust potential" of this
event has notably increased. Nonetheless, given the susceptibility
of the Moderate Risk area to flash flooding in both aforementioned
urban centers and along the Atchafalaya River and its spillways,
the current forecasted rainfall during this period, though almost
entirely Wednesday morning, would still likely cause numerous
instances of flash flooding, some of whom may be significant.

Regardless of exactly where the heaviest storms are occurring at
the start of the period Wednesday morning, there is very good
consensus that by as early as late Wednesday morning, the storms
will have all pushed south into the Gulf, leaving much of the
Louisiana coast in much lighter outflow from those storms to the
north of their cores. Thus, most of the threat is prior to 18Z,
with very likely downgrades likely thereafter.

Further to the west, the Slight Risk area was expanded west to
include the Houston metro in coordination with HGX/Houston, TX
forecast office. The aforementioned southward trend in the
guidance is notable here as well, but there appears to be better
consensus there may be newly developed afternoon convection
impacting the Houston Metro Wednesday afternoon. Urbanization and susceptibility to flash flooding of that area was a considerable
factor in the upgrade for this area.

...Mid-South...

An expansive Marginal Risk area was added with this update from
Kansas to north Georgia ahead of a dying upper level low that will
slowly track eastward across the region, providing enough forcing
for widely scattered thunderstorms to take advantage of still
considerable Gulf moisture in the area. Much of this area has been
hit recently with heavy rains, which will locally increase the
flash flooding risk, especially if the upper low can help organize
any of the convection.

...Florida Space Coast...

A small Marginal Risk was added to the ERO for urbanized portions
of the I-95 corridor through north Florida along the Space Coast. A
stalled out cold front is likely to provide enough forcing given
the plentiful moisture around (PWATs exceeding 1.75 inches) to
allow any storms that form, perhaps along the sea breeze or along
the cold pools of other storms, to be slow moving and have enough
moisture to locally cause heavy rains. Isolated instances of flash
flooding are possible.

Wegman

...Previous Discussion...

By Wednesday, the warm front that lifted through the Upper Texas
coast will stall out along the Gulf Coast and be the focus for
widespread showers and thunderstorms. PWs remain above the 97.5
climatological percentiles from the Upper Texas coast to as far
east as the FL Panhandle. In fact, there are anomalous PWs that
stretch up into northern AL Wednesday afternoon. The flash flood
threat remains greatest along the central Gulf Coast and Lower
MS Valley regions where they are most commonly positioned at the
nose of a >500 kg/m/s IVT and PWs that are topping 1.75" in most
locations. RAP soundings in southern LA Wednesday morning show
low-mid level RH values >90% and warm cloud layers at least
11,000ft deep. These soundings also depict tall "skinny CAPE"
profiles with MLCAPE >500 J/kg. Plus, hodographs still suggest the
potential for organized convection given modest mid-level shear and
low-level helicity (sfc-3km >150 m2/s2). The NBM 75th percentile
shows rainfall totals >5" in some cases across the central Gulf
Coast, which is on top of the heavy rainfall that occurred on
Tuesday. The concern would be the SWrly IVT continues to intersect
the stalled frontal boundary in a way that supports training and
back-building convection that produces highly efficient rainfall
rates >2"/hr over soils that are increasingly saturated. No
Moderate Risk was hoisted as of this forecast cycle as there are
still some varying scenarios depicted by model guidance, but should
guidance come into better agreement on a swath of 3-5" amounts
and./or soils grow highly sensitive due to Tuesday's Excessive
Rainfall, a Moderate Risk upgrade could be necessary.

The Marginal Risk was expanded north into the hills of northern AL
where FFGs are lower (<2" for 1-hr FFGs) and guidance showed some
modest moisture advection via the aforementioned IVT. Given the
saturated soils in the region and the potential for locally heavy
rainfall rates, the Marginal Risk was expanded a little farther
north closer ot the TN Valley.

Mullinax

Day 3
Valid 12Z Thu May 08 2025 - 12Z Fri May 09 2025

...THERE IS A SLIGHT RISK OF EXCESSIVE RAINFALL OVER PORTIONS OF
THE CENTRAL GULF COAST...

...2030Z Update...

...Central Gulf Coast...

In coordination with LIX/Slidell, LA forecast office, a Slight Risk
upgrade was introduced with this update for portions of the central
Gulf Coast. The stalled front over the area will continue to
provide the forcing needed for additional convection to form along
the coast, possibly intruding inland as far north as New Orleans.
The area is expected to be very susceptible to flash flooding from
additional rainfall after today's and Wednesday's storms, but it's
very possible that the strongest storms impacting the area remain
offshore enough to not pose as high a flash flooding risk. However,
despite this uncertainty with where the storms will form countered
with the certainty that the soils and rivers will be full from
prior days' rainfall, there's enough certainty for the risk
upgrade.

...Southeast...

The Marginal Risk was expanded along Florida's First and Space
Coasts as well as northwest into Arkansas with this update. A
longwave very positively tilted trough will continue to provide the
forcing needed for another day of convective development across the
Southeast as plentiful Gulf moisture remains south of the surface
cold front. Due to the diffuse nature of the front and low
predictability of any surface fronts and cold pools, expect the
storms to be mostly disorganized and widely scattered, which favors
the Marginal Risk mostly for areas where the soils are more
saturated due to prior rains. For Florida, the same front will be
stuck along the coast as the Day 2/Wednesday period, resulting in
the potential for similar convection again in this period Thursday
afternoon.

...Deep South Texas...

A broad Marginal was added with this update on the tail end of the
front over the western Gulf and into Texas. A significant cold
front pushing south out of central Texas will meet up with deep
Gulf moisture over the western Gulf, which will allow for scattered
storms across the area, which will force additional convection from
prior storms' cold pools. This most areas will see at least some
period of heavy rain, which will be capable of causing isolated
instances of flash flooding.

...Northeast...

A very potent digging shortwave trough will move due south down the Appalachians on Thursday. It will tap into increasing Gulf/Atlantic
moisture downwind of the Gulf convection, drawing moisture and
instability northward and into the Northeast, with the shortwave
providing the forcing. Instability will be the limiting factor for
any storms, with the initial development of those storms perhaps
having the greatest flash flooding threat. By the overnight
Thursday night, expect a broad swath of moderate rainfall with
embedded convection tracking northward into the Northeast. Once
again some of these same areas have had or are having heavy rain
impact the area the past couple days through the Day 2 period, so
isolated instance of flash flooding in this area appear likely with
the additional rainfall.

Wegman

...Previous Discussion...

...Central Gulf Coast...

Thursday and into Thursday night is a near carbon-copy setup to
Wednesday's where the stationary front draped W-E along the Gulf
Coast will continue to act as the initiator in additional
thunderstorms across the South. The central Gulf Coast will remain
the more primed spot for potential flash flooding given the
increasingly sensitive soils in the region after multiple days of
heavy rainfall. PWs ranging between 1.6-1.8" will be common with
MLCAPE that tops 1,000 J/kg. Thunderstorms could produce >2"/hr
rainfall rates across the Marginal Risk area. Should guidance trend
wetter in the coming days, it is possible a Slight Risk upgrade may
be necessary given the soils more sensitive state.

...Northeast...

No Marginal Risk was introduced tonight, but this region bears
watching as a cold front approaches from the West. Several guidance
members now show 1-2" of rainfall across portions of the region on
Thursday, however they vary on where those heavier amounts are most
likely to occur. A positively tilted upper trough approaching from
Ontario will provide plenty of upper-level ascent while the
approaching cold front acts as the surface/low-level trigger for
initiating thunderstorms. Plus, some guidance members show the positively-tilted trough cutting off just enough to where an 850mb
low forms near the Northeast coast. This is not the case across all
guidance and is resulting in rainfall swaths that are farther
north over the interior Northeast (GFS/ECMWF/ICON), or as far
south and east as the I-95 corridor (EC-AIFS/CMC/UKMET/RRFS). With
lingering uncertainty in the forecast, the Marginal Risk upgrade
was held off this forecast cycle. But given the highly saturated
soils in the region, it is possible a Marginal Risk will be
necessary in future forecast updates once confidence increases in
where the heaviest swath of rainfall occurs.


Mullinax


Day 1 threat area: https://urldefense.com/v3/__https://www.wpc.ncep.noaa.go= v/qpf/94epoints.txt__;!!DZ3fjg!_n2TqWAnQKR7c8FnLUDnecZ19sdECMCVJtdC3Llzj-lf= t5UxFN3QI5LKkRtKPDxRNilmT-KdJ7GN5BcGdSYs-IEruYQ$=20
Day 2 threat area: https://urldefense.com/v3/__https://www.wpc.ncep.noaa.go= v/qpf/98epoints.txt__;!!DZ3fjg!_n2TqWAnQKR7c8FnLUDnecZ19sdECMCVJtdC3Llzj-lf= t5UxFN3QI5LKkRtKPDxRNilmT-KdJ7GN5BcGdSYszD3tjhQ$=20
Day 3 threat area: https://urldefense.com/v3/__https://www.wpc.ncep.noaa.go= v/qpf/99epoints.txt__;!!DZ3fjg!_n2TqWAnQKR7c8FnLUDnecZ19sdECMCVJtdC3Llzj-lf= t5UxFN3QI5LKkRtKPDxRNilmT-KdJ7GN5BcGdSYsLvflM8E$=20

=3D =3D =3D
To unsubscribe from WX-STORM and you already have a login, go to https://lists.illinois.edu and use the "Unsubscribe" link. Otherwise email Chris Novy at cnovy@cox.net and ask to be removed from WX-STORM.

--- SBBSecho 3.20-Linux
* Origin: capitolcityonline.net * Telnet/SSH:2022/HTTP (1:2320/105)

FOUS30 KWBC 070818
QPFERD

Excessive Rainfall Discussion
NWS Weather Prediction Center College Park MD
418 AM EDT Wed May 7 2025

Day 1
Valid 12Z Wed May 07 2025 - 12Z Thu May 08 2025

...THERE IS A MODERATE RISK OF EXCESSIVE RAINFALL FOR PORTIONS OF
SOUTHERN LOUISIANA...

...Gulf Coast...

The warm front that lifted through the Upper Texas coast has
stalled along the Gulf Coast and be the focus for widespread=20
showers and thunderstorms through this morning. PWs remain above=20
the 97.5 climatological percentiles from the Upper TX coast to=20
southern LA. The flash flood threat remains greatest along the=20
central Gulf Coast and Lower MS Valley regions where they are most=20
commonly positioned at the nose of a >500 kg/m/s IVT and PWs that=20
are approaching 2.0" along the LA coast. RAP soundings in southern=20
LA Wednesday morning show low-mid level RH values >90% and warm=20
cloud layers at least 11,000ft deep. These soundings also depict=20
tall "skinny CAPE" profiles with MLCAPE >500 J/kg. Plus, hodographs
still suggest the potential for organized convection given modest=20
mid-level shear and low-level helicity (sfc-3km >100 m2/s2). The=20
SWrly IVT will intersect the stalled frontal boundary in a way that
supports training and back-building convection producing highly=20
efficient rainfall rates >2"/hr over soils that are increasingly=20
saturated. This supports the lingering presence of the Moderate=20
Risk in southern LA through the first half of the day. Note that=20
most model guidance has the bulk of the Day 1 Excessive Rainfall=20
threat during the morning hours. There may still be some residual=20 thunderstorm activity through the afternoon, but most guidance=20
suggests the bulk of the flash flood threat should wind down some
for the second half of the day.

Further to the west, the Slight Risk remains in place for the
Houston metro given the greater urbanization and susceptibility to
flash flooding. There is the potential for another round of storms
this afternoon that will track over a similar area that was hit by
heavy rainfall yesterday, but any lingering flash flood threat=20
should begin to wind down after sunset.

...Central Plains & Mid-South...

The lingering mid-upper level low circulation of the Central=20
Plains will funnel a narrow swath of 700-300mb moisture along the=20
northern flank of the low, while weak 850mb FGEN and WAA over the=20
Mid-South. Despite the lack of modest instability, RAP soundings=20
show >90% saturated sfc-700mb profiles and warm cloud layers up to
9,000ft deep in some cases. With modest upper-level and mesoscale=20
forcing present, as well as ample low-mid level moisture, efficient
rainfall over saturated soils in parts of the region could result=20
in additional areas of flash flooding. Aside from minor tweaks to=20
the area given the latest QPF, the Marginal Risk remains on track.=20

...Florida Space Coast...

A small Marginal Risk remains in place for urbanized portions of=20
the I-95 corridor through north Florida along the Space Coast. A=20
stalled out cold front to the north and typical sea breeze cycles
will trigger rounds of thunderstorms that will have unusually high
PWs available by early May climo in eastern FL. PWs are generally
above 1.75" in northern FL, which is above the 97.5 climatological
percentile according to ECMWF SATs. 00Z RAP soundings for=20
Wednesday afternoon show highly saturated profiles (>90% within=20
the sfc-500mb layer), skinny CAPE soundings with >1,000 J/kg of=20
MLCAPE, and warm cloud layers of at least 12,000ft deep. Most=20
rainfall will be a welcome sight for the region with severe to=20
extreme drought having set in. However, the soils are so dry that=20
rainfall rates >2"/hr would prove too much for the sandy soils of=20
northern FL to handle, let alone the more urbanized corridor along=20
I-95. Isolated instances of flash flooding are possible, with the=20
more urbanized communities most at-risk.

Mullinax

Day 2
Valid 12Z Thu May 08 2025 - 12Z Fri May 09 2025

...THERE ARE SLIGHT RISKS OF EXCESSIVE RAINFALL OVER PORTIONS OF=20
THE CENTRAL GULF COAST & THE NORTHEAST...

...Central Gulf Coast & Southeast...

The stalled front draped north of the Gulf Coast will continue to
act as a trigger for additional thunderstorms on Thursday. In
addition to what is still a moist air-mass for early May, there
will be the added assistance of an approaching positively-tilted
500mb trough to provide additional upper-level support. The central
Gulf Coast remains most susceptible to flash flooding given their
closer positioning to a >400 kg/m/s IVT and PWs above 1.75". These
favorable atmospheric parameters are on top of what are now highly
sensitive soils following multiple days worth of heavy rainfall.
The Slight Risk remains in place over a small section of the
Central Gulf Coast, while the expansive Marginal Risk that
stretches from the Ozarks to as far east as the Southeast coast=20
still looks to be in good shape given the dearth of moisture in=20
place ahead of the approaching cold front and sufficient=20
instability (MLCAPE between 500-1,500 J/kg). The FL Space Coast is=20
also at risk for flash flooding given the similar setup to=20
Wednesday and potential for more saturated soils following any=20
thunderstorm activity on Wednesday. Localized flash flooding is=20
possible, most notably in the region's more urbanized communities=20
and where PWs are highest.

...Deep South Texas...

A strong cold front pushing south out of central Texas will meet=20
up with Gulf moisture, resulting in scattered thunderstorms across
the area. These storms will have the benefit of a dual-jet streak
setup aloft which when combined with the approach of a 500mb
shortwave trough will help support thunderstorm clusters into
Thursday night. Low-level easterly winds should lead to=20
thunderstorm development over the Davis Mountains that could then=20
propagate SE towards the Rio Grande Valley. With mean wind flow=20
out of the west, any storms that may form over the Sierra Madre=20
could also approach the Rio Grande River Thursday evening. As these
initial round of storms generate cold pools, these new cold pools=20
will invigorate additional clusters of storms Thursday night. Most=20
areas will see at least some period of heavy rain, which will be=20
capable of causing isolated instances of flash flooding.

...Northeast...

A complex upper-level evolution will begin on Thursday over the
Northeast that is trending towards a more wet and stormy setup
across the Northeast. An anti-cyclonic wave break over southeast
Canada is splitting a lobe of the positively-tilted upper trough over
southern Ontario into a cut-off low by Thursday night. Guidance
remains split on how far west the blossoming shield of
precipitation will advance, but most guidance is coming into a
consensus on a swath of the Northeast that stems from central PA=20
and the southern tier of NY on east into areas just west of I-95.
The area of greatest concern lies in northeast PA and into the
Catskills where soils have grown exceptionally sensitive over the
past several days thanks to multiple rounds of heavy rainfall.=20

As the upper low deepens Thursday night, strong 200-500mb upper
level divergence will work in tandem with strengthening 850-700mb
FGEN and WAA to generate an axis of heavy rainfall. Soundings
between 06-12Z Fri show highly saturated profiles and warm cloud
layers as deep as 9,000ft deep closer to I-95. As of this
discussion, 6-hr FFGs were as low as 1.00" along the northeast
PA/NY state borders. While some recovery is expected, this
highlights that it may not take much more than one inch of rainfall
in 6 hours to cause flash flooding. For these reasons, a Slight=20
Risk was introduced over parts of the Poconos and Catskills where=20
there is a decent compromise for higher QPF and where soils are=20
most sensitive.

Mullinax

Day 3
Valid 12Z Fri May 08 2025 - 12Z Sat May 09 2025

...THERE IS A SLIGHT RISK OF EXCESSIVE RAINFALL OVER PORTIONS OF
THE CENTRAL GULF COAST...

...Gulf Coast & Southeast...

An amplifying and large upper low positioned over the Lower MS
Valley will linger over the region through Friday night with heavy
rainfall likely from the central Gulf Coast to the Southeast coast.
Latest trends in guidance has been to sharpen up a 500mb low over
the Lower MS Valley. The ECMWF SATs page shows an IVT >400 kg/m/s
which is above the 90th climatological percentile. Soundings in the
region also show highly saturated profiles, modest instability,=20
and deep warm cloud layers. This combined with sufficient vertical=20
wind shear to help sustain areas of organized thunderstorms is=20
increasing the threat for Excessive Rainfall over the central Gulf=20
Coast and FL Panhandle. This setup remains fluid given the recent=20
trends in guidance to be wetter over the central Gulf Coast, with=20
the EC- AIFS and GFS GraphCast showing similar trends. Given the=20
growing soil sensitivities in the central Gulf Coast, the latest=20
Day 3 ERO update now includes a Slight Risk. The more urbanized=20
swath of the I-10 corridor is most at-risk for potential flash=20
flooding on Friday.=20

...Northeast...

The upper-low evolution stated in the Day 2 discussion holds true
for Friday but unlike Day 2 when the heavy rain threat is confined
to a 6 to at most 12 hour window, the Excessive Rainfall threat
will impact not just the daytime hours on Friday but into Friday
night. Out ahead of the upper low, guidance is showing a
strengthening IVT surpassing 500 kg/m/s off the Northeast coast
that will transport copious amounts of moisture into the Northeast.
Moisture will wrap around the northern flank of the 500mb low into
northern NY and central New England. Farther east, the warm sector
will feature highly saturated and deep warm cloud layers that could
contain some weak elevated instability. There remains some spread=20
in where the axis of heaviest rainfall sets up, which is why a=20
Slight Risk was not issued as of this forecast cycle. However,=20
given trends in guidance are all pointing towards a cut-off low=20
over the Northeast and soils throughout the region are highly=20
sensitive, there may be the need for a Slight Risk upgrade in=20
future forecast updates once confidence increases in where the=20
heaviest rainfall takes shape.=20

Mullinax


Day 1 threat area: https://urldefense.com/v3/__https://www.wpc.ncep.noaa.go= v/qpf/94epoints.txt__;!!DZ3fjg!5rZh7KSfG4xdx58B-Hc8O8lD5mzA848TbA7ptpOJt2K6= d6nIwgURD1fUy8ePSiER5l5cV3AgJ6LoitVYqKop0MiyFOs$=20
Day 2 threat area: https://urldefense.com/v3/__https://www.wpc.ncep.noaa.go= v/qpf/98epoints.txt__;!!DZ3fjg!5rZh7KSfG4xdx58B-Hc8O8lD5mzA848TbA7ptpOJt2K6= d6nIwgURD1fUy8ePSiER5l5cV3AgJ6LoitVYqKopGAUGy3U$=20
Day 3 threat area: https://urldefense.com/v3/__https://www.wpc.ncep.noaa.go= v/qpf/99epoints.txt__;!!DZ3fjg!5rZh7KSfG4xdx58B-Hc8O8lD5mzA848TbA7ptpOJt2K6= d6nIwgURD1fUy8ePSiER5l5cV3AgJ6LoitVYqKopXRfRgn4$=20

=3D =3D =3D
To unsubscribe from WX-STORM and you already have a login, go to https://lists.illinois.edu and use the "Unsubscribe" link. Otherwise email Chris Novy at cnovy@cox.net and ask to be removed from WX-STORM.

--- SBBSecho 3.20-Linux
* Origin: capitolcityonline.net * Telnet/SSH:2022/HTTP (1:2320/105)

FOUS30 KWBC 071557
QPFERD

Excessive Rainfall Discussion
NWS Weather Prediction Center College Park MD
1157 AM EDT Wed May 7 2025

Day 1
Valid 16Z Wed May 07 2025 - 12Z Thu May 08 2025

...THERE IS A MODERATE RISK OF EXCESSIVE RAINFALL FOR PORTIONS OF
SOUTHERN LOUISIANA...

...Gulf Coast...

16Z update... The cluster of convection has mostly progressed out
of Texas with intensity decreasing over western Louisiana noted as
well. As such, the Marginal Risk area was reduced to the Galveston
area and points east. The Slight Risk was trimmed out of southwest
Louisiana. Currently there is a squall line over the central Gulf
that will continue to impact south-central and southeast Louisiana
over the next few hours. A Moderate Risk was already in place
however was adjusted to include the city of New Orleans. The
progressive nature of this convection may warrant a special update
to address the reduction of threat for flash flooding as the storms
dissipate and/or move out of the area.

Campbell

The warm front that lifted through the Upper Texas coast has
stalled along the Gulf Coast and be the focus for widespread
showers and thunderstorms through this morning. PWs remain above
the 97.5 climatological percentiles from the Upper TX coast to
southern LA. The flash flood threat remains greatest along the
central Gulf Coast and Lower MS Valley regions where they are most
commonly positioned at the nose of a >500 kg/m/s IVT and PWs that
are approaching 2.0" along the LA coast. RAP soundings in southern
LA Wednesday morning show low-mid level RH values >90% and warm
cloud layers at least 11,000ft deep. These soundings also depict
tall "skinny CAPE" profiles with MLCAPE >500 J/kg. Plus, hodographs
still suggest the potential for organized convection given modest
mid-level shear and low-level helicity (sfc-3km >100 m2/s2). The
SWrly IVT will intersect the stalled frontal boundary in a way that
supports training and back-building convection producing highly
efficient rainfall rates >2"/hr over soils that are increasingly
saturated. This supports the lingering presence of the Moderate
Risk in southern LA through the first half of the day. Note that
most model guidance has the bulk of the Day 1 Excessive Rainfall
threat during the morning hours. There may still be some residual
thunderstorm activity through the afternoon, but most guidance
suggests the bulk of the flash flood threat should wind down some
for the second half of the day.

Further to the west, the Slight Risk remains in place for the
Houston metro given the greater urbanization and susceptibility to
flash flooding. There is the potential for another round of storms
this afternoon that will track over a similar area that was hit by
heavy rainfall yesterday, but any lingering flash flood threat
should begin to wind down after sunset.

...Central Plains & Mid-South...

The lingering mid-upper level low circulation of the Central
Plains will funnel a narrow swath of 700-300mb moisture along the
northern flank of the low, while weak 850mb FGEN and WAA over the
Mid-South. Despite the lack of modest instability, RAP soundings
show >90% saturated sfc-700mb profiles and warm cloud layers up to
9,000ft deep in some cases. With modest upper-level and mesoscale
forcing present, as well as ample low-mid level moisture, efficient
rainfall over saturated soils in parts of the region could result
in additional areas of flash flooding. Aside from minor tweaks to
the area given the latest QPF, the Marginal Risk remains on track.

...Georgia and northeast Florida...

16Z update... The latest CAMs have trended the convection a bit
further north placing them from northeast Florida up the coast
toward the South Carolina/Georgia line. Georgia was previously not
included in the Marginal Risk area and has now been added. Portions
of the central Florida coast was removed from the Marginal as well.=20

Campbell

A small Marginal Risk remains in place for urbanized portions of
the I-95 corridor through north Florida along the Space Coast. A
stalled out cold front to the north and typical sea breeze cycles
will trigger rounds of thunderstorms that will have unusually high
PWs available by early May climo in eastern FL. PWs are generally
above 1.75" in northern FL, which is above the 97.5 climatological
percentile according to ECMWF SATs. 00Z RAP soundings for
Wednesday afternoon show highly saturated profiles (>90% within
the sfc-500mb layer), skinny CAPE soundings with >1,000 J/kg of
MLCAPE, and warm cloud layers of at least 12,000ft deep. Most
rainfall will be a welcome sight for the region with severe to
extreme drought having set in. However, the soils are so dry that
rainfall rates >2"/hr would prove too much for the sandy soils of
northern FL to handle, let alone the more urbanized corridor along
I-95. Isolated instances of flash flooding are possible, with the
more urbanized communities most at-risk.

Mullinax

Day 2
Valid 12Z Thu May 08 2025 - 12Z Fri May 09 2025

...THERE ARE SLIGHT RISKS OF EXCESSIVE RAINFALL OVER PORTIONS OF
THE CENTRAL GULF COAST & THE NORTHEAST...

...Central Gulf Coast & Southeast...

The stalled front draped north of the Gulf Coast will continue to
act as a trigger for additional thunderstorms on Thursday. In
addition to what is still a moist air-mass for early May, there
will be the added assistance of an approaching positively-tilted
500mb trough to provide additional upper-level support. The central
Gulf Coast remains most susceptible to flash flooding given their
closer positioning to a >400 kg/m/s IVT and PWs above 1.75". These
favorable atmospheric parameters are on top of what are now highly
sensitive soils following multiple days worth of heavy rainfall.
The Slight Risk remains in place over a small section of the
Central Gulf Coast, while the expansive Marginal Risk that
stretches from the Ozarks to as far east as the Southeast coast
still looks to be in good shape given the dearth of moisture in
place ahead of the approaching cold front and sufficient
instability (MLCAPE between 500-1,500 J/kg). The FL Space Coast is
also at risk for flash flooding given the similar setup to
Wednesday and potential for more saturated soils following any
thunderstorm activity on Wednesday. Localized flash flooding is
possible, most notably in the region's more urbanized communities
and where PWs are highest.

...Deep South Texas...

A strong cold front pushing south out of central Texas will meet
up with Gulf moisture, resulting in scattered thunderstorms across
the area. These storms will have the benefit of a dual-jet streak
setup aloft which when combined with the approach of a 500mb
shortwave trough will help support thunderstorm clusters into
Thursday night. Low-level easterly winds should lead to
thunderstorm development over the Davis Mountains that could then
propagate SE towards the Rio Grande Valley. With mean wind flow
out of the west, any storms that may form over the Sierra Madre
could also approach the Rio Grande River Thursday evening. As these
initial round of storms generate cold pools, these new cold pools
will invigorate additional clusters of storms Thursday night. Most
areas will see at least some period of heavy rain, which will be
capable of causing isolated instances of flash flooding.

...Northeast...

A complex upper-level evolution will begin on Thursday over the
Northeast that is trending towards a more wet and stormy setup
across the Northeast. An anti-cyclonic wave break over southeast
Canada is splitting a lobe of the positively-tilted upper trough over
southern Ontario into a cut-off low by Thursday night. Guidance
remains split on how far west the blossoming shield of
precipitation will advance, but most guidance is coming into a
consensus on a swath of the Northeast that stems from central PA
and the southern tier of NY on east into areas just west of I-95.
The area of greatest concern lies in northeast PA and into the
Catskills where soils have grown exceptionally sensitive over the
past several days thanks to multiple rounds of heavy rainfall.

As the upper low deepens Thursday night, strong 200-500mb upper
level divergence will work in tandem with strengthening 850-700mb
FGEN and WAA to generate an axis of heavy rainfall. Soundings
between 06-12Z Fri show highly saturated profiles and warm cloud
layers as deep as 9,000ft deep closer to I-95. As of this
discussion, 6-hr FFGs were as low as 1.00" along the northeast
PA/NY state borders. While some recovery is expected, this
highlights that it may not take much more than one inch of rainfall
in 6 hours to cause flash flooding. For these reasons, a Slight
Risk was introduced over parts of the Poconos and Catskills where
there is a decent compromise for higher QPF and where soils are
most sensitive.

Mullinax

Day 3
Valid 12Z Fri May 09 2025 - 12Z Sat May 10 2025

...THERE IS A SLIGHT RISK OF EXCESSIVE RAINFALL OVER PORTIONS OF
THE CENTRAL GULF COAST...

...Gulf Coast & Southeast...

An amplifying and large upper low positioned over the Lower MS
Valley will linger over the region through Friday night with heavy
rainfall likely from the central Gulf Coast to the Southeast coast.
Latest trends in guidance has been to sharpen up a 500mb low over
the Lower MS Valley. The ECMWF SATs page shows an IVT >400 kg/m/s
which is above the 90th climatological percentile. Soundings in the
region also show highly saturated profiles, modest instability,
and deep warm cloud layers. This combined with sufficient vertical
wind shear to help sustain areas of organized thunderstorms is
increasing the threat for Excessive Rainfall over the central Gulf
Coast and FL Panhandle. This setup remains fluid given the recent
trends in guidance to be wetter over the central Gulf Coast, with
the EC- AIFS and GFS GraphCast showing similar trends. Given the
growing soil sensitivities in the central Gulf Coast, the latest
Day 3 ERO update now includes a Slight Risk. The more urbanized
swath of the I-10 corridor is most at-risk for potential flash
flooding on Friday.

...Northeast...

The upper-low evolution stated in the Day 2 discussion holds true
for Friday but unlike Day 2 when the heavy rain threat is confined
to a 6 to at most 12 hour window, the Excessive Rainfall threat
will impact not just the daytime hours on Friday but into Friday
night. Out ahead of the upper low, guidance is showing a
strengthening IVT surpassing 500 kg/m/s off the Northeast coast
that will transport copious amounts of moisture into the Northeast.
Moisture will wrap around the northern flank of the 500mb low into
northern NY and central New England. Farther east, the warm sector
will feature highly saturated and deep warm cloud layers that could
contain some weak elevated instability. There remains some spread
in where the axis of heaviest rainfall sets up, which is why a
Slight Risk was not issued as of this forecast cycle. However,
given trends in guidance are all pointing towards a cut-off low
over the Northeast and soils throughout the region are highly
sensitive, there may be the need for a Slight Risk upgrade in
future forecast updates once confidence increases in where the
heaviest rainfall takes shape.

Mullinax


Day 1 threat area: https://urldefense.com/v3/__https://www.wpc.ncep.noaa.go= v/qpf/94epoints.txt__;!!DZ3fjg!9p1PvlyvH3Or29dc9Ooph-46iF-XzReFhuxGQEV8OiBd= T4DNvnjdFM-4_uErgsn8VuNPWphu0qAgP1e_xAUV5t7MxKk$=20
Day 2 threat area: https://urldefense.com/v3/__https://www.wpc.ncep.noaa.go= v/qpf/98epoints.txt__;!!DZ3fjg!9p1PvlyvH3Or29dc9Ooph-46iF-XzReFhuxGQEV8OiBd= T4DNvnjdFM-4_uErgsn8VuNPWphu0qAgP1e_xAUVfWjohs0$=20
Day 3 threat area: https://urldefense.com/v3/__https://www.wpc.ncep.noaa.go= v/qpf/99epoints.txt__;!!DZ3fjg!9p1PvlyvH3Or29dc9Ooph-46iF-XzReFhuxGQEV8OiBd= T4DNvnjdFM-4_uErgsn8VuNPWphu0qAgP1e_xAUVrqPO4UI$=20

=3D =3D =3D
To unsubscribe from WX-STORM and you already have a login, go to https://lists.illinois.edu and use the "Unsubscribe" link. Otherwise email Chris Novy at cnovy@cox.net and ask to be removed from WX-STORM.

--- SBBSecho 3.20-Linux
* Origin: capitolcityonline.net * Telnet/SSH:2022/HTTP (1:2320/105)

FOUS30 KWBC 071819
QPFERD

Excessive Rainfall Discussion
NWS Weather Prediction Center College Park MD
219 PM EDT Wed May 7 2025

Day 1
Valid 16Z Wed May 07 2025 - 12Z Thu May 08 2025

...THERE IS A MODERATE RISK OF EXCESSIVE RAINFALL FOR PORTIONS OF
SOUTHERN LOUISIANA...

...Gulf Coast...

18Z Update... The heaviest rainfall has now pushed firmly off the
Central Gulf coast with the theta_E alignment now running parallel,
offshore of the coastal plain leading to remnant stratiform
precipitation across Southeast LA. Some pockets of moderate to
heavy rain are still plausible south of the I-10 corridor over LA
leaving a low-end MRGL in place for the rest of the afternoon
before the event fully subsides. Considering the above factors and
limitations on the potential, the previous SLGT and MDT risks were
removed in coordination with the local WFO with a small MRGL in
place to cover for the remaining precip bands moving over the
region.=20

Kleebauer

16Z update... The cluster of convection has mostly progressed out
of Texas with intensity decreasing over western Louisiana noted as
well. As such, the Marginal Risk area was reduced to the Galveston
area and points east. The Slight Risk was trimmed out of southwest
Louisiana. Currently there is a squall line over the central Gulf
that will continue to impact south-central and southeast Louisiana
over the next few hours. A Moderate Risk was already in place
however was adjusted to include the city of New Orleans. The
progressive nature of this convection may warrant a special update
to address the reduction of threat for flash flooding as the storms
dissipate and/or move out of the area.

Campbell

The warm front that lifted through the Upper Texas coast has
stalled along the Gulf Coast and be the focus for widespread
showers and thunderstorms through this morning. PWs remain above
the 97.5 climatological percentiles from the Upper TX coast to
southern LA. The flash flood threat remains greatest along the
central Gulf Coast and Lower MS Valley regions where they are most
commonly positioned at the nose of a >500 kg/m/s IVT and PWs that
are approaching 2.0" along the LA coast. RAP soundings in southern
LA Wednesday morning show low-mid level RH values >90% and warm
cloud layers at least 11,000ft deep. These soundings also depict
tall "skinny CAPE" profiles with MLCAPE >500 J/kg. Plus, hodographs
still suggest the potential for organized convection given modest
mid-level shear and low-level helicity (sfc-3km >100 m2/s2). The
SWrly IVT will intersect the stalled frontal boundary in a way that
supports training and back-building convection producing highly
efficient rainfall rates >2"/hr over soils that are increasingly
saturated. This supports the lingering presence of the Moderate
Risk in southern LA through the first half of the day. Note that
most model guidance has the bulk of the Day 1 Excessive Rainfall
threat during the morning hours. There may still be some residual
thunderstorm activity through the afternoon, but most guidance
suggests the bulk of the flash flood threat should wind down some
for the second half of the day.

Further to the west, the Slight Risk remains in place for the
Houston metro given the greater urbanization and susceptibility to
flash flooding. There is the potential for another round of storms
this afternoon that will track over a similar area that was hit by
heavy rainfall yesterday, but any lingering flash flood threat
should begin to wind down after sunset.

...Central Plains & Mid-South...

The lingering mid-upper level low circulation of the Central
Plains will funnel a narrow swath of 700-300mb moisture along the
northern flank of the low, while weak 850mb FGEN and WAA over the
Mid-South. Despite the lack of modest instability, RAP soundings
show >90% saturated sfc-700mb profiles and warm cloud layers up to
9,000ft deep in some cases. With modest upper-level and mesoscale
forcing present, as well as ample low-mid level moisture, efficient
rainfall over saturated soils in parts of the region could result
in additional areas of flash flooding. Aside from minor tweaks to
the area given the latest QPF, the Marginal Risk remains on track.

...Georgia and northeast Florida...

16Z update... The latest CAMs have trended the convection a bit
further north placing them from northeast Florida up the coast
toward the South Carolina/Georgia line. Georgia was previously not
included in the Marginal Risk area and has now been added. Portions
of the central Florida coast was removed from the Marginal as well.

Campbell

A small Marginal Risk remains in place for urbanized portions of
the I-95 corridor through north Florida along the Space Coast. A
stalled out cold front to the north and typical sea breeze cycles
will trigger rounds of thunderstorms that will have unusually high
PWs available by early May climo in eastern FL. PWs are generally
above 1.75" in northern FL, which is above the 97.5 climatological
percentile according to ECMWF SATs. 00Z RAP soundings for
Wednesday afternoon show highly saturated profiles (>90% within
the sfc-500mb layer), skinny CAPE soundings with >1,000 J/kg of
MLCAPE, and warm cloud layers of at least 12,000ft deep. Most
rainfall will be a welcome sight for the region with severe to
extreme drought having set in. However, the soils are so dry that
rainfall rates >2"/hr would prove too much for the sandy soils of
northern FL to handle, let alone the more urbanized corridor along
I-95. Isolated instances of flash flooding are possible, with the
more urbanized communities most at-risk.

Mullinax

Day 2
Valid 12Z Thu May 08 2025 - 12Z Fri May 09 2025

...THERE ARE SLIGHT RISKS OF EXCESSIVE RAINFALL OVER PORTIONS OF
THE CENTRAL GULF COAST & THE NORTHEAST...

...Central Gulf Coast & Southeast...

The stalled front draped north of the Gulf Coast will continue to
act as a trigger for additional thunderstorms on Thursday. In
addition to what is still a moist air-mass for early May, there
will be the added assistance of an approaching positively-tilted
500mb trough to provide additional upper-level support. The central
Gulf Coast remains most susceptible to flash flooding given their
closer positioning to a >400 kg/m/s IVT and PWs above 1.75". These
favorable atmospheric parameters are on top of what are now highly
sensitive soils following multiple days worth of heavy rainfall.
The Slight Risk remains in place over a small section of the
Central Gulf Coast, while the expansive Marginal Risk that
stretches from the Ozarks to as far east as the Southeast coast
still looks to be in good shape given the dearth of moisture in
place ahead of the approaching cold front and sufficient
instability (MLCAPE between 500-1,500 J/kg). The FL Space Coast is
also at risk for flash flooding given the similar setup to
Wednesday and potential for more saturated soils following any
thunderstorm activity on Wednesday. Localized flash flooding is
possible, most notably in the region's more urbanized communities
and where PWs are highest.

...Deep South Texas...

A strong cold front pushing south out of central Texas will meet
up with Gulf moisture, resulting in scattered thunderstorms across
the area. These storms will have the benefit of a dual-jet streak
setup aloft which when combined with the approach of a 500mb
shortwave trough will help support thunderstorm clusters into
Thursday night. Low-level easterly winds should lead to
thunderstorm development over the Davis Mountains that could then
propagate SE towards the Rio Grande Valley. With mean wind flow
out of the west, any storms that may form over the Sierra Madre
could also approach the Rio Grande River Thursday evening. As these
initial round of storms generate cold pools, these new cold pools
will invigorate additional clusters of storms Thursday night. Most
areas will see at least some period of heavy rain, which will be
capable of causing isolated instances of flash flooding.

...Northeast...

A complex upper-level evolution will begin on Thursday over the
Northeast that is trending towards a more wet and stormy setup
across the Northeast. An anti-cyclonic wave break over southeast
Canada is splitting a lobe of the positively-tilted upper trough over
southern Ontario into a cut-off low by Thursday night. Guidance
remains split on how far west the blossoming shield of
precipitation will advance, but most guidance is coming into a
consensus on a swath of the Northeast that stems from central PA
and the southern tier of NY on east into areas just west of I-95.
The area of greatest concern lies in northeast PA and into the
Catskills where soils have grown exceptionally sensitive over the
past several days thanks to multiple rounds of heavy rainfall.

As the upper low deepens Thursday night, strong 200-500mb upper
level divergence will work in tandem with strengthening 850-700mb
FGEN and WAA to generate an axis of heavy rainfall. Soundings
between 06-12Z Fri show highly saturated profiles and warm cloud
layers as deep as 9,000ft deep closer to I-95. As of this
discussion, 6-hr FFGs were as low as 1.00" along the northeast
PA/NY state borders. While some recovery is expected, this
highlights that it may not take much more than one inch of rainfall
in 6 hours to cause flash flooding. For these reasons, a Slight
Risk was introduced over parts of the Poconos and Catskills where
there is a decent compromise for higher QPF and where soils are
most sensitive.

Mullinax

Day 3
Valid 12Z Fri May 09 2025 - 12Z Sat May 10 2025

...THERE IS A SLIGHT RISK OF EXCESSIVE RAINFALL OVER PORTIONS OF
THE CENTRAL GULF COAST...

...Gulf Coast & Southeast...

An amplifying and large upper low positioned over the Lower MS
Valley will linger over the region through Friday night with heavy
rainfall likely from the central Gulf Coast to the Southeast coast.
Latest trends in guidance has been to sharpen up a 500mb low over
the Lower MS Valley. The ECMWF SATs page shows an IVT >400 kg/m/s
which is above the 90th climatological percentile. Soundings in the
region also show highly saturated profiles, modest instability,
and deep warm cloud layers. This combined with sufficient vertical
wind shear to help sustain areas of organized thunderstorms is
increasing the threat for Excessive Rainfall over the central Gulf
Coast and FL Panhandle. This setup remains fluid given the recent
trends in guidance to be wetter over the central Gulf Coast, with
the EC- AIFS and GFS GraphCast showing similar trends. Given the
growing soil sensitivities in the central Gulf Coast, the latest
Day 3 ERO update now includes a Slight Risk. The more urbanized
swath of the I-10 corridor is most at-risk for potential flash
flooding on Friday.

...Northeast...

The upper-low evolution stated in the Day 2 discussion holds true
for Friday but unlike Day 2 when the heavy rain threat is confined
to a 6 to at most 12 hour window, the Excessive Rainfall threat
will impact not just the daytime hours on Friday but into Friday
night. Out ahead of the upper low, guidance is showing a
strengthening IVT surpassing 500 kg/m/s off the Northeast coast
that will transport copious amounts of moisture into the Northeast.
Moisture will wrap around the northern flank of the 500mb low into
northern NY and central New England. Farther east, the warm sector
will feature highly saturated and deep warm cloud layers that could
contain some weak elevated instability. There remains some spread
in where the axis of heaviest rainfall sets up, which is why a
Slight Risk was not issued as of this forecast cycle. However,
given trends in guidance are all pointing towards a cut-off low
over the Northeast and soils throughout the region are highly
sensitive, there may be the need for a Slight Risk upgrade in
future forecast updates once confidence increases in where the
heaviest rainfall takes shape.

Mullinax


Day 1 threat area: https://urldefense.com/v3/__https://www.wpc.ncep.noaa.go= v/qpf/94epoints.txt__;!!DZ3fjg!-xxYvunSc3Nypsta0TXHvLCSiCxTYI1O_OyeXRoXL0dr= ui9U3MZ8KuYCfjIueHdXVuP3fMheFfFlMvYKQoIMnGoSM_Y$=20
Day 2 threat area: https://urldefense.com/v3/__https://www.wpc.ncep.noaa.go= v/qpf/98epoints.txt__;!!DZ3fjg!-xxYvunSc3Nypsta0TXHvLCSiCxTYI1O_OyeXRoXL0dr= ui9U3MZ8KuYCfjIueHdXVuP3fMheFfFlMvYKQoIMK2bVtCQ$=20
Day 3 threat area: https://urldefense.com/v3/__https://www.wpc.ncep.noaa.go= v/qpf/99epoints.txt__;!!DZ3fjg!-xxYvunSc3Nypsta0TXHvLCSiCxTYI1O_OyeXRoXL0dr= ui9U3MZ8KuYCfjIueHdXVuP3fMheFfFlMvYKQoIMpM95tVg$=20

=3D =3D =3D
To unsubscribe from WX-STORM and you already have a login, go to https://lists.illinois.edu and use the "Unsubscribe" link. Otherwise email Chris Novy at cnovy@cox.net and ask to be removed from WX-STORM.

--- SBBSecho 3.20-Linux
* Origin: capitolcityonline.net * Telnet/SSH:2022/HTTP (1:2320/105)