777
AWUS01 KWNH 261908
FFGMPD
TXZ000-270105-

Mesoscale Precipitation Discussion 1383
NWS Weather Prediction Center College Park MD
307 PM EDT Sat Sep 26 2026

Areas affected...western TX/Big Bend

Concerning...Heavy rainfall...Flash flooding possible

Valid 261905Z - 270105Z

SUMMARY...Slow moving thunderstorms may result in isolated flash
flooding across portions of western TX into the Big Bend region
through this evening. Peak hourly rainfall of 1 to 2 inches
(locally higher) with isolated storm totals near 3 inches will be
possible.

DISCUSSION...GOES East visible imagery from 1840Z showed building
cumulus across the higher terrain of the Trans Pecos region of
western TX along with early convective development near the Glass
Mountains. This region was devoid of larger scale forcing with
mean westerly flow aloft noted on water vapor imagery, in the wake
of a departing shortwave across the central Plains. Moisture was
anomalous however, with the 12Z MAF and DRT soundings showing 1.6
to 2.0 inches of precipitable water (near the climatological max
for late September). This moisture was largely focused in the low
to mid levels with increasingly drier upper levels as one moves
northwest into southeastern NM per the latest layered PW imagery.

Deeper layer steering flow was 10-15 kt from the west near
Midland-Odessa and weakened to the south near 5 kt at Big Bend
N.P. Clear skies have helped contribute to 1000-2000 J/kg MLCAPE
via the 18Z SPC mesoanalysis, focused along a weakly defined low
level convergence axis which extended from near Big Bend to near
MAF to near CDS. Better moisture was located east of the low level
convergence axis with drier air to the west.

Continued daytime heating will likely contribute to scattered
thunderstorms by 21Z across western TX into the Big Bend region
with the environment supportive of hourly rainfall between 1-2
inches (isolated higher possible). An increase in low level
convergence is expected along the trough axis toward 00Z which
should support a SW to NE axis of thunderstorms by this evening
into northwestern TX, but the flash flood concern is currently
greatest with the slower cell motions to the south. Surface
dewpoint depressions of 20-30 degrees may allow for numerous
outflow boundaries but with slow cell motions and additional
thunderstorm development, isolated flash flooding could occur
across locally sensitive terrain or overlap of any population
centers.

Otto

...Please see www.wpc.ncep.noaa.gov for graphic product...

ATTN...WFO...MAF...SJT...

ATTN...RFC...FWR...NWC...

LAT...LON   32250177 31950104 31160103 30150198 29630243
            29080281 28900336 29290441 30050498 31200474
            31720328 32210248