193
AWUS01 KWNH 031135
FFGMPD
TXZ000-031700-

Mesoscale Precipitation Discussion 0577
NWS Weather Prediction Center College Park MD
734 AM EDT Thu Jul 03 2025

Areas affected...Portions of West Texas from the Big Bend through
the Edwards Plateaui

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

Valid 031134Z - 031700Z

Summary...Showers and thunderstorms are expected to increase in
coverage this morning and move slowly across parts of West Texas.
Rainfall rates at times may reach 1-2"/hr, leading to 1-3" of
rain. Flash flooding is possible.

Discussion...The GOES-E IR imagery this morning shows an expanding
area of cooling cloud tops over the Mexican state of Coahuila in
response to a potent shortwave lifting northward over the
Serranias del Burro. These cooling cloud tops are associated with
intensifying convection approaching the Big Bend of Texas, and
although reflectivity over the area is sparse at this time, the
GOES-E GREMLIN radar emulation appears to match the IR imagery
quite nicely showing higher reflectivity lifting towards the
international border. At the same time, showers have begun to
develop across the Edwards Plateau in response to a plume of
increasing MUCAPE of 1000-2000 J/kg collocated with PWs that are
analyzed by the SPC RAP to be 1.8 to 2.2 inches, or above the 99th
percentile, thanks in part to a connection to tropical moisture
associated with Tropical Storm Flossie over the Eastern Pacific
noted via the ALPW products.

Although the CAMs are struggling to resolve the ongoing activity,
and admittedly are not exceptionally aggressive with rainfall the
next few hours, the environment and evolution support heavy
rainfall through the morning. Low-level S/SE flow measured at
850mb on the VWPs at both DFX and MAF are around 20 kts, which is
helping to transport the elevated PWs northward, and this flow may
be locally accelerated downstream of the approaching shortwave.
This will help to further improve the local thermodynamic
environment, while at the same time leading to locally enhanced
convergence into the mean wind which is generally around 10 kts.
This evolution suggests that storms will increase in coverage
(with additional ascent provided via the shortwave itself) and
then move slowly/chaotically as Corfidi vectors veer strongly to
the right of the mean wind and bulk shear remains minimal.
Although the CAMs are not initializing very well, the accompanying
HREF and REFS ensemble solutions do indicate increasing coverage
of 10-30% probabilities for 1"/hr rates, leading to 1-3" of rain
with isolated higher amounts.

FFG across the region is highly variable due a wide variation in
7-day rainfall, but in some places the 3-hr FFG is as low as 1.5
inches, and 0-40cm soil moisture just north of the international
border is above the 95th percentile. This indicates that some
areas are locally vulnerable to rapid runoff, so as storms spread
northward and expand/intensify, instances of flash flooding could
result.


Weiss

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

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

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

LAT...LON   32390144 32240056 31970032 31319998 30569973
            29989966 29399983 28950014 28870061 29200124
            29440185 29150266 28960313 28870351 29080407
            29500445 29710463 30180465 30640416 31200337
            31350324 32100231