Mesoscale Precipitation Discussion 0712
NWS Weather Prediction Center College Park MD
430 AM EDT Tue Jul 14 2026

Areas affected...TX Hill Country...South-Central to Southeast
TX...Southwest LA

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

Valid 140830Z - 141430Z

SUMMARY...Increasing coverage of showers and thunderstorms with
locally extreme rainfall rates will foster a likelihood for seeing
areas of flash flooding going into the morning hours. Potential
will exist for locally significant and life-threatening impacts.

DISCUSSION...The predawn GOES-E Proxy Visible satellite imagery
shows an elongated axis of mid-level energy extending from the TX
Hill Country eastward across southeast TX and into southwest LA.
This includes placement of a mid-level low center over eastern TX
to the north of Houston, and an increasingly well-defined vort
center in close proximity to the TX Hill Country.

This energy will be interacting with a gradual increase in south
to southwest low-level flow near and along multiple surface
troughs to promote developing and expanding clusters of showers
and thunderstorms. Already the latest radar and satellite imagery
is confirming an uptick in convective activity at the regional
level.

The latest RAP analysis shows an uncapped and very moist/unstable
airmass pooled across south-central to southeast TX with a rather
strong instability gradient noted along the inverted trough that
is situated south of San Antonio and extending over toward the
middle and upper TX coast along with far southwest LA. Increasing
moist/unstable flow advancing into and poleward of this boundary
is expected to help facilitate the expansion of convection over
the next several hours.

MLCAPE values of 1500 to 2500 J/kg are in place locally, with PWs
running as high as 2.25 to 2.5 inches. 3-hour MLCAPE and PW
differentials show this moisture and instability becoming better
established with time, which includes the pooling of this moisture
and instability off to the northwest into parts of the TX Hill
Country near the aforementioned vort center along with a separate
surface trough.

The latest hires CAMs led by the HRRR/RRFS and experimental WoFS,
and the earlier 00Z HREF/REFS suites, suggest a regional increase
in convective activity with rainfall rates capable of reaching 2
to 4 inches/hour with the stronger convective cells. Already
storms overnight west of San Antonio had a history of producing
these extreme rates. The slow cell-motions and potential for
cell-anchoring near these surface troughs will support the
potential this morning for localized 4 to 6+ inch rainfall totals.

Given the local sensitivities of the TX Hill Country and the urban
corridors, areas of flash flooding are likely this morning. Some
of this may be significant and life-threatening.

Orrison

ATTN...WFO...CRP...EWX...FWD...HGX...LCH...MAF...SHV...SJT...

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

LAT...LON   31559444 31309327 30509213 29919172 29389203
            29449358 29019475 28529614 28629834 28519942
            28570051 29300141 29810242 30420268 31080209
            31350036 31279864 31219715 31289582