431
AWUS01 KWNH 141315
FFGMPD
TXZ000-141814-

Mesoscale Precipitation Discussion 0683
NWS Weather Prediction Center College Park MD
914 AM EDT Mon Jul 14 2025

Areas affected...South Central TX

Concerning...Heavy rainfall...Flash flooding likely

Valid 141314Z - 141814Z

SUMMARY...Flash flood threat continues across portions of south
central TX into the southern Hill Country. Locally significant
impacts remain possible.

DISCUSSION...Recent radar and IR satellite imagery continue to
depict deep convection over portions of south central TX from the
Rio Grande into the southern Hill Country region. This activity is
focused near a compact MCV, which has been nearly stationary, but
should gradually shift north or northeast today. Around 20kts of
southerly inflow into this MCV continues to result in areas of
slow moving and/or backbuilding convection. The mid morning hours
are a tricky time of day for MCV driven convection, as the
tendency is for a weakening trend as diurnal heating results in a
weakening of the low level jet and also convergence near the MCV.
However there are some signs that convection this morning may try
to persist, as modeled 850mb flow really does not weaken all that
much...staying close to 20kts. Certainly will have plenty of
instability to the south, and PWs between 2" and 2.25", so the
thermodynamic ingredients will remain favorable for excessive
rainfall. The MCV and convection is positioned within a favorably
divergent region of upper level flow as well, which is likely
aiding in sustaining deep convection. Thus the main question for
maintenance going forward is whether we have enough low level
convergence to keep activity organized.

Some weakening of this convergence is expected over the next
couple hours...as is typical for this time of day. However, given
the aforementioned persistence of southerly low level inflow into
the MCV, it does seem like some persistence or reinvigoration of
convection is possible this morning. Confidence is low on exactly
how widespread and organized convection will end up being...but
would expect some of areas of flash flooding to continue. Recent
HRRR runs do indeed show some persistence to this training
convection.

Deep layer mean flow is southerly around 15kt...but upwind
propagation vectors are northerly around 10kts. This is a
favorable orientation for backbuilding convection. Given the
ingredients in place, continued areas of significant flash
flooding remain possible this morning. The hope is we will see
some diurnal weakening of activity...but as the HRRR
indicates...even if that occurs we could still see some additional
convective development feeding into the MCV as the morning
progresses. With areas of flash flooding ongoing, confidence is
high on the threat continuing a couple more hours. However,
confidence is lower on whether we see continued development
through the morning or a gradual dissipation of the stronger
cores. But the potential for continued development leading to
additional locally significant flash flooding is enough to warrant
keeping a close eye on trends through the morning hours. The
general trend should continue to favor any backbuilding on the
southern edge of the convective complex...but as the MCV drifts
north it is possible we also see some gradual northward expansion
of heavier rainfall rates this morning.

Chenard

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

ATTN...WFO...EWX...

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

LAT...LON   30179995 30049940 29489917 28869936 28599987
            28570045 28870088 29150098 29380109 29610120
            29960108 30060068 30110045