Mesoscale Precipitation Discussion 0582
NWS Weather Prediction Center College Park MD
710 PM EDT Thu Jul 03 2025

Areas affected...Texas Hill Country

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

Valid 032300Z - 040500Z

SUMMARY...Concerning trends for back-building and training
thunderstorms over the Texas Hill Country this evening that could
produce >3"/hr max rainfall rates.

DISCUSSION...The remnant mid-level circulation associated with
Barry (also classified as an MCV on the graphic) is over western
Texas and slowly approaching the Texas Hill Country this evening.
Barry's remnant circulation has an abundance of atmospheric
moisture at its disposal with PWs ranging anywhere from 2.2-2.5".
ECMWF ENS percentiles show these PWs above the 99th climatological
percentile, as are the mean specific humidity (g/kg) values at
both the 850mb and 500mb height levels. The atmosphere is also
quite unstable with MUCAPE generally between 2,000-3,000 J/kg. As
night falls, the low-level jet (LLJ) will gradually accelerate out
of South Texas and intersect the Hill Country in a manner that
supports topographically-forced ascent. This low-level jet is also
part of a fairly strong southerly IVT for early July as the ECMWF
ENS percentiles depict >500 kg/m/s values (above the 97.5
climatological percentile) over the Hill Country between 00-06Z.
The impressive moisture advection is making for some remarkably
saturated RAP soundings where low-mid level RH values are >90% and
warm cloud layers are 15,000ft deep in many cases.

The concern with the MCV and remnant 500-700mb trough is that it
is paired with a persistent LLJ that looks to be steadfast over
the region well into the overnight hours. While there is not a ton
of vertical wind shear, noticeable veering in the sfc-3km layer
ensues as the LLJ strengthens this evening (SErly sfc winds, SWrly
3km winds). This could provide cells with the ability to be
somewhat self-sustaining and organized this evening. The other
concern is for outflows associated with a growing cold pool from
northerly convection to propagate south and be oriented in a way
where the southerly LLJ intersects the outflows in a perpendicular
fashion. The atmospheric parameters are supportive of not just the
potential for >3"/hr maximum rainfall rates, but for back-building
and training thunderstorms over the Hill Country.

The I-35 corridor on west is most at-risk for flash flooding
tonight. 1-hr FFGs are generally between 1.5-2.0" in portions of
the Hill Country, which given the prolific rainfall potential
these storms may contain, would have little problem causing flash
flooding. For areas where back-building and training storms do
occur, locally considerable flash flooding this evening is
possible.

Mullinax

ATTN...WFO...EWX...FWD...SJT...

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

LAT...LON   33049861 32029772 30809750 29669772 29079855
            29169957 29860011 30700023 31420008 32959969