FOUS30 KWBC 260747
QPFERD

Excessive Rainfall Discussion
NWS Weather Prediction Center College Park MD
347 AM EDT Tue May 26 2026

Day 1
Valid 12Z Tue May 26 2026 - 12Z Wed May 27 2026

...THERE IS A SLIGHT RISK OF EXCESSIVE RAINFALL ACROSS PORTIONS OF
THE CENTRAL GULF COAST, AND CENTRAL TO WEST TEXAS...

...Texas...

Current WV satellite and upper air analysis indicates a broad,
negatively- tilted trough axis migrating eastward out of the
Southwestern CONUS into the Southern High Plains this evening. A
broad diffluent pattern exists downstream of the mean trough with
several small mid-level perturbations causing a panoply of
convectively driven cells to materialize across the terrain of
eastern NM, spreading eastward into the adjacent High Plains as
surface troughing exists over southwest TX up through the eastern
NM plains. Increased large scale ascent will become fixated over
much of west TX, spreading further through the High Plains as
widespread shower and thunderstorm activity continues through the
morning and afternoon hours today. A plethora of convective
activity with relatively slow to modest propagation speeds will
translate into bouts of heavier rainfall across the southern half
of the TX Panhandle down through the Permian Basin and western
Rolling Plains the first half of the period leading to rainfall
totals between 1-3" over the aforementioned areas. Greatest
opportunity for flash flooding will exist across urbanized settings
and areas where copious low water crossings are present, creating
drainage concerns on a localized scale.

As we step into the late-morning and early afternoon time frame,
the focus will shift south into the Pecos River Valley and adjacent
Stockton Plateau where convection will initiate off the dryline
situated over the area with assistance from an approaching
shortwave sliding eastward out of Chihuahua. Ample shear and
favorable instability fields reflect the initiation of
supercellular storm modes with additional multi-cell development
along and ahead of the dryline leading to strong cell cores capable
of heavy rainfall as the environmental moisture anomalies sit
firmly between +1 to +2 deviations above climo. Storm motion
vectors maintain a relatively steady forward propagation to the
east and southeast from the initiation point allowing for a trail
of significant rain totals between 1-3", locally higher to
materialize from the southern Permian Basin down through the
Stockton Plateau, Lower Trans Pecos, and eventually into the mid
and lower Concho Valley by the evening. This setup is classic for
scattered flash flood instances, especially in those more urban
zones and areas of high low water crossing concentrations that are
littered over the above zones, albeit this potential is greater
than what will occur a bit further north. This reflected well
within the 00z HREF neighborhood and EAS prob fields pertaining to
the >2" threshold where both probabilities remain elevated area
wide, but a notable maxima is positioned over the Lower Trans Pecos
and those areas surrounding within the Permian Basin and Concho
Valley. The maxima extends into the northern Edwards Plateau, a
likely conjecture that correlates to the proposed motion of the
expected complex of thunderstorms motioning out from areas to the
west-northwest. This zone is part of a larger areal extent of heavy
rainfall anticipated for the period with a second axis likely to
materialize after sunset.

Rainfall will likely be winding down in areas west TX that are
located along and west of the Pecos River after 00z Wednesday, but
the setup will shift focus into more of a nocturnal issue as we
pivot our attention south over the central RGV as a strong mid-
level vorticity maxima ejects out of Coahuila later this evening
and slides east into the Edwards Plateau and neighboring Hill
Country. There's a general consensus on this setup across guidance
with some degree of broad heavy convection migrating into the
above areas enticing a dousing of rainfall as the pattern evolves
overnight. We'll see the introduction of a LLJ only add to the low-
level convergence regime spurred on by the expected evolution
likely allowing quite the rainfall signature in wake of the
disturbance's trajectory. US57 to I-10 is the prospectus area of
interest, which includes much of southern and central Hill Country
with the very end of the period likely to see some of the activity
make it beyond the I-35 corridor near San Antonio and even make
headway towards Corpus Christi. The highest confidence area
according to the neighborhood probability fields for >3" remains
over the Hill Country to the I-35 corridor between Austin to San
Antonio with the maximum (40-60%) located in those areas just west
of the metro corridor along and near I-10. Probabilities for >5" do
drop off significantly to <20% everywhere with a majority of the
probs closer to 10%, so the magnitude within guidance is relatively
consistent with a signature of 2-4" with locally up to 5" in the
hardest hit areas. This is still plentiful to cause problems when
it occurs, so the threat is well within the bounds of a SLGT, even
leaning towards the higher end of the threshold for flash flooding.
This area up through the southern Permian Basin and Stockton
Plateau will be monitored closely for any potential targeted
upgrades in future updates.

The SLGT risk encompasses a broad area of TX spanning much of west
TX all the way to about 75 miles east of I-35 with the northern
periphery right up against the Red River and the southern points
running from Corpus Christi to near Laredo.

...Southeast to Mid Atlantic...

Confluent area on the western edge of a broad Western Atlantic
ridge and a trough centered over the Southern Plains will continue
for at least one more period with another round of convergence and
heavy convection focused over the Central Gulf Coast to areas
inland between southeast MS into the southern half of AL. This area
will have seen multiple days of impact from heavier convection to
begin with, so current priming of the soils could enact a greater
flash flood potential in general with an emphasis on areas that
received 3+ inches over the last 24 hours. Highest probabilities
for >3" reside across the corridor extending from New Orleans over
through Mobile into the western FL Panhandle and points just north
of I-10. This area has received considerable rainfall the past 24
hours with some places in the FL Panhandle receiving over 6 inches
of rainfall the past few days. Despite what was a drier environment
heading into the weekend, this area is sufficiently saturated in
the top soil layer leading to greater run off capabilities as we
step through today. The greatest axis of convergence within the
hi-res suite has been pin-pointed over the western FL Panhandle
where >5" neighborhood probs are running as high as 40-50% for a
small area between Pensacola to west of Tallahassee, including
Panama City beach along the coast. Radar analysis this evening is a
pretty good indication of the persistent southerly flow off the
Gulf in this narrow corridor, so this area in particular is one to
watch for the period. This area over to New Orleans is well defined
into the SLGT risk with a higher-end of the risk threshold forecast
for this zone.

Further north, the confluent pattern on the western edge of the
ridge up to the frontal alignment in the Mid Atlantic stands to be
a focal point for another day of scattered to widespread convection
with general rates between 1-2"/hr across the Appalachian front and
1-3"/hr in the adjacent lower elevations located over GA/SC/NC/VA.
These areas have been hit multiple times the past few days with
several flash flood warnings issued due to the convective impacts
the past 24 hours. This only stands to continue for another period
given pattern persistence, so wanted to make sure this was
reflected in the new D1 issuance. In coordination with several
offices across the Southeast to Mid Atlantic, a SLGT risk expansion
was noted up through the aforementioned areas of the Southern
Appalachians into the neighboring Piedmont of the Carolina's,
southern VA, and most of the northern half of GA.

...Northern Rockies...

Energetic disturbance ejecting out of the Pacific Northwest and
British Columbia will make headway into the Northern Rockies by
later this afternoon leading to a period of convective activity to
spawn along the Lewis Range down into the high valleys of western
MT. PWATs running over 1" across the Northern Rockies is well above
climo norms, closer to the 99th percentile as noted by the latest
NAEFS outputs, more than sufficient to be a problem for any more
sensitive topographic features present given the complex
topography. Multiple burn scars in the area will also be under
threat for seeing rainfall rates between 0.5-1"/hr at times, a
threshold that could cause rapid run off and debris flows if cells
linger over the sensitive areas. This is not a widespread flash
flood prospect, but isolated to widely scattered instances cannot
be ruled out considering the above environment. A MRGL risk remains
in place to account for the lower end threat.

Kleebauer
$$
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 * Origin: Project Scorpio TEST (618:250/6)