Mesoscale Precipitation Discussion 0937
NWS Weather Prediction Center College Park MD
907 PM EDT Sun Oct 07 2018

Areas affected...Rio Grande Valley to the TX Hill Country

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

Valid 080105Z - 080705Z

Summary...Heavy showers and thunderstorms are expected to become
more concentrated over the next few hours. Very heavy rainfall
rates will likely result in flash flooding.

Discussion...The latest satellite imagery shows a strongly
divergent flow pattern aloft within what is a very moist and
moderately unstable airmass across the middle and lower Rio Grande
Valley. Showers and thunderstorms have been gradually developing
north of the middle Rio Grande Valley and are lifting north toward
portions of the TX Hill Country. MUCAPE values are running as high
as 2000+ j/kg and PWATS are as high as 1.8 to 2.0 inches.

The latest hires model guidance consisting of the 12Z
ARW/ARW2/NMMB solutions and recent HRRR runs support an axis of
highly focused convection setting up over the next several hours
along and adjacent an axis from Del Rio to Rocksprings to
Junction, TX involving areas of the Rio Grande Valley and the TX
Hill Country. Much of the activity should be enhanced by
additional shortwave energy lifting northeast across mainland
Mexico ahead of a deep layer trough over the Southwest U.S. This
energy will maintain favorable right-entrance region jet dynamics
across the region within a favorable thermodynamic regime over the
next several hours. There will likely be evolution of convective
cold pools to that will foster additional low level support/focus
for convection.

Rainfall amounts of as much as 2 inches/hr will be possible as
convection organizes, and storm totals to as much as 4 to 6 inches
will be possible through 06Z. These amounts are likely to cause
flash flooding overnight. Will continue to closesly monitor.

Orrison

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

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

LAT...LON   31269960 31049869 29999899 29309953 29020024
            29110059 29620076 30140064 30750025