Excessive Rainfall Discussion
NWS Weather Prediction Center College Park MD
1159 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, CENTRAL TO WEST TEXAS AND THE OHIO 
VALLEY...

...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 to Ohio Valley...

16Z update... A Slight Risk was hoisted for portions of the Ohio
Valley along the stalled west-east frontal boundary, from southeast
Missouri to eastern Kentucky. Scattered to widespread convection
have been lifting through the region this morning over sensitive
soils. Local 1hr/3hr FFGs are as low as 1/1.5 inches and with
hourly rates pulsating up to 1.5-2+ inches/hr over this part of the
country could quickly reach or exceed the FFGs.

Minor westward adjustment to the Slight Risk over
eastern Louisiana was made to reflect the latest QPF guidance and
trends. The Gulf Coast and into western Georgia is where much of
the CAMs are focusing narrow streaks of heavy to intense rainfall 
for this period with accumulations of 2-3+ inches.

Campbell

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...

16Z update... Convection this morning has been firing up across
eastern Washington and northern Idaho, areas very similar in 
topography with sensitive locations as described below. The western
boundary of the Marginal Risk was expanded into eastern Washington
to cover this convection and more expected later in the day.

Campbell

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


Day 2
Valid 12Z Wed May 27 2026 - 12Z Thu May 28 2026

...THERE IS A SLIGHT RISK OF EXCESSIVE RAINFALL ACROSS THE EASTERN
HALF OF TEXAS, PORTIONS OF THE LOWER MISSISSIPPI VALLEY, AND AREAS
OF THE OHIO VALLEY TO CENTRAL APPALACHIANS...

...Texas to Lower Mississippi Valley...

The broad upper level evolution occurring upstream over the
Southern Plains will continue to shift east with the large scale
forcing driving into the eastern half of TX leading to heavy rain
prospects over the eastern portions of Hill Country, the I-35
corridor and much of east TX, including the middle and upper TX
coastal areas on Wednesday. Environmental conditions for heavy
rainfall are most favorable along the TX and LA Gulf coast areas
with a corridor of elevated theta_E's aligned from Corpus Christi
up through the Lower Sabine to about 100 miles inland. The setup is
contingent on the behavior of the convective pattern upstream into
the central portion of the state and the migration of the
thunderstorm complex exiting out of I-35. The general consensus is
the maxima for precip will likely occur in proximity to the same
areas that were hit within the past week; the area along the upper
TX coast from Houston up to Lake Charles. This is very well defined
within the probability fields in both the HREF and the AIFS-ENS
where >3" is likely (60-90%) within the confines of that zone with
the HREF even signaling modest >5" potential (40-60%) in that same
zone. There's still some uncertainty in the behavior of any
mesoscale complexes that end up materializing from all the
convective development the previous evening and if they cause any
significant shifts in the potential. In this case, this leads to a
broad SLGT risk with a MRGL risk encompassing over the Southern
Plains to Lower Mississippi Valley as broad upper forcing will
likely spur scattered convection all across areas from western KS
down through OK in the setup. Areas away from east TX and the Lower
Mississippi will have more isolated heavy rain prospects,
comparatively, so the threat remains elevated in the SLGT risk
within these particular locations.

...Ohio Valley...

Conditions will become increasingly favorable for heavy rainfall
across the Ohio Valley going into Wednesday from a multitude of
features that will ultimately couple into something more formidable
during peak diurnal instability. Sheared vorticity stemming from
previous period convection will likely settle over the central Ohio
Valley with a west to east bisecting quasi-stationary front
positioned just north of the Ohio River basin. A sweeping trough
exiting out of Ontario will help tighten an axis of confluence
across the Midwest and Ohio Valley by Wednesday afternoon, enticing
a squeeze of the thermal gradient and regional instability axis
that aligns with the frontal placement. Destabilization by the
afternoon hours will lead to scattered to widespread thunderstorm
initiation along the boundary with convective episodes likely to
spawn heavier cells capable of hourly rates between 1-2"/hr as PWAT
anomalies sit firmly within +2 standard deviations above climo.
Previous periods of rainfall in the last three to four days have
really brought down the areal FFG markers for all 1/3/6 hour
thresholds with a vast majority of places along the Ohio River
basin and points north running <1"/hr in the hourly exceedance
indicator. This points to any heavier convective impacts could
cause issues with the remnant soil moisture and hydrologic
concerns that are lingering after the last event. This is
especially true for eastern OH, southwest PA, and western WV where
complex topography only exacerbate the potential in these zones.
3-hour FFG exceedance probabilities from the 00z HREF are between
20-40% for a large portion of eastern IN through the southern half
of OH into southwest PA with a maxima of 40-60% located across
northwest WV between US50 and WV7. Considering the antecedent
conditions and expected widespread convective regime along the
front, a SLGT risk was added for an increasing threat for flash
flooding Wednesday.

Kleebauer


Day 3
Valid 12Z Thu May 28 2026 - 12Z Fri May 29 2026

...THERE IS A MARGINAL RISK OF EXCESSIVE RAINFALL ACROSS PORTIONS
OF THE CENTRAL AND SOUTHERN PLAINS, LOWER MISSISSIPPI VALLEY, AND
SOUTHEAST FLORIDA...

...Plains to Lower Mississippi Valley...

Breakdown of the persistent pattern for areas east of the
Continental Divide will lead to weaker steering flow, but still
enough moisture, lingering boundaries, and remnant mid-level
vorticity to spur up bouts of scattered convection all across parts
of the Central and Southern Plains into the Mississippi Valley.
This setup is a far cry from what we've experienced the past
several days, so the prospects of widespread flash flooding are
much lower comparatively. However, environmental conditions and
deep moisture presence still remain favorable along the northern
periphery of the trough lingering across east TX which places the
best opportunity for convective episodes to be located over the
aforementioned areas. Ensemble QPF footprint is most notable across
the Central Gulf coast and upper TX coastal plain, likely in part
to the positioning of the trough and the fact the most prevalent
theta_E is situated along the immediate Gulf. It's a period to
monitor for any small scale features that could enhance convective
potential further, but for now, a broad MRGL exists to cover for
the threat.

...Florida...

Active sea breeze pattern with weakening steering flow will lead to
a period of heavy rainfall across the southeast FL coast on
Thursday afternoon. Consensus within guidance is for an active
period between 18-00z Thu/Fri that would allow for heavy convection
with slow forward propagations to impact the South Florida metro
corridor from West Palm Beach down to Miami. Globals and regional
guidance even have some 2+" totals already in the output, and
that's before the CAM's even have a depiction. Typically, this is a
sign for heavy rainfall prospects capable of flash flooding,
especially when you consider the PWATs running +1 to +2 deviations
across that area of the Peninsula. A MRGL risk remains for that
urban corridor of southeastern FL.

Kleebauer


Day 1 threat area: https://www.wpc.ncep.noaa.gov/qpf/94epoints.txt
Day 2 threat area: https://www.wpc.ncep.noaa.gov/qpf/98epoints.txt
Day 3 threat area: https://www.wpc.ncep.noaa.gov/qpf/99epoints.txt