Mesoscale Precipitation Discussion 0102
NWS Weather Prediction Center College Park MD
325 PM EDT Fri Mar 15 2024

Areas affected...Portions of South-Central to Southeast TX

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

Valid 151925Z - 160125Z

SUMMARY...Showers and thunderstorms will be developing and
expanding in coverage over the next several hours. Very heavy
rainfall rates and locally slow cell-motions are expected to drive
concerns for isolated to widely scattered instances of flash
flooding.

DISCUSSION...The latest GOES-East visible satellite imagery is
showing an increasingly unstable boundary layer across much of
south-central to southeast TX as strong diurnal heating occurs in
conjunction with the pooling of low-level moisture out ahead of a
slow-moving cold front.

MLCAPE values have increased to as much as 2000 to 3000 J/kg and
the latest CIRA-ALPW data shows a strong concentration of moisture
in the SFC-850 layer. This coupled with frontal convergence and
relatively strong shear parameters should set the stage for the
development and expansion of rather organized convective activity,
including a mix of multicell and supercell thunderstorms. Already
the latest dual-pol radar in conjunction with satellite imagery is
showing areas of convective initiation underway.

Rainfall rates with some of the stronger and more organized cells
may reach 2.5"/hour, and with rather slow cell-motions expected,
some rainfall totals may reach 3 to 5 inches in as little as 2 to
3 hours. The 12Z HREF guidance was somewhat indeterminate on the
location of the heaviest rainfall, but recent runs of the HRRR
guidance have been trending wetter and generally favor an axis
from east of San Antonio to north of Victoria and potentially in
time getting into the western suburbs of the Houston metropolitan
area going through 00Z (7PM CDT).

The convective threat will also in time extend farther west to
areas closer to the Lower Rio Grande Valley including areas such
as Uvalde and Cotulla as the cold front continues to edge
southward and interacts with what should be a strongly unstable
boundary layer heading through the late-afternoon and early
evening hours. Isolated to widely scattered instances of flash
flooding will be possible given the expected high rainfall rates
and short-term storm totals.

Orrison

ATTN...WFO...CRP...EWX...HGX...LCH...

ATTN...RFC...WGRFC...NWC...

LAT...LON   30619504 30399443 29859440 29489453 28889561
            28359754 28109913 28180006 28650055 29170021
            29489934 29839793 30379648