SPC MD 272

MD 0272 CONCERNING SEVERE POTENTIAL...WATCH LIKELY FOR PORTIONS OF SOUTHERN TX

Mesoscale Discussion 0272
NWS Storm Prediction Center Norman OK
0100 AM CDT Sun Apr 07 2019

Areas affected...portions of southern TX

Concerning...Severe potential...Watch likely 

Valid 070600Z - 070730Z

Probability of Watch Issuance...80 percent

SUMMARY...Large hail and damaging wind gusts will be possible
overnight into the early morning hours across much of southern Texas
as a cluster of storms in Mexico cross the Rio Grande and shift
eastward.

DISCUSSION...The severe threat will continue to increase overnight
as a cluster of storms over the higher terrain of Mexico shifts east
across parts of the Hill Country and points south. This convection
is being forced by increasing ascent as the southern stream
shortwave trough ejects over northern Mexico. The downstream
environment is characterized by a very moist boundary layer with
upper 60s to low 70s dewpoints beneath midlevel lapse rates around
8-8.5 C/km. This is resulting in MUCAPE values around 2000-3000
J/kg. Low level easterly flow through the lowest 1km or so is
relatively weak, ranging from about 10-15 kt, but should increase
slightly with time. A quasi-stationary front is draped across the
region from northern Maverick County east/northeast into
east-central TX. Hi-res guidance suggests convection will organize
and travel roughly along and south of this boundary in the more
pristine warm sector airmass. 

Given very steep midlevel lapse rates, hail will be likely in
embedded stronger updrafts/supercells. Storm mode could temper a
more significant hail threat, though some very large hail cannot be
ruled out. While boundary layer inhibition is quite strong at this
point, strong forcing should be sufficient to weaken low level
inhibition sufficiently for some damaging wind threat as well.
Convection will track eastward across much of southern TX through
the overnight hours and a watch will be within the next hour or so.

..Leitman/Thompson.. 04/07/2019

...Please see www.spc.noaa.gov for graphic product...

ATTN...WFO...CRP...EWX...BRO...

LAT...LON   29639872 29629810 29469749 29079701 28759675 28489660
            28239656 27969685 27659711 27429731 27249753 27139787
            27159887 27259947 27589973 27799995 28080014 28270035
            28610053 29080073 29260063 29460013 29639872 

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from SPC Forecast Products http://www.spc.noaa.gov/products/md/md0272.html