Subj : MESO: Nws Weather Prediction Center College Park Md
To   : wx-storm@lists.illinois.edu
From : COD Weather Processor
Date : Tue May 09 2023 01:24:31

AWUS01 KWNH 090124
FFGMPD
TXZ000-090722-

Mesoscale Precipitation Discussion 0241
NWS Weather Prediction Center College Park MD
923 PM EDT Mon May 08 2023

Areas affected...TX Hill Country through South-Central TX and the
Lower Rio Grande Valley

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

Valid 090122Z - 090722Z

SUMMARY...Isolated to widely scattered instances of flash flooding
will be possible going into the overnight hours from expanding
clusters of showers and thunderstorms.

DISCUSSION...Early evening satellite imagery shows a well-defined
mid-level shortwave trough over northern Mexico that will be
crossing the Rio Grande Valley and advancing northeast into areas
of the TX Hill Country and south-central TX going into the
overnight hours.

Forcing associated with this energy will be interacting with a
moist and unstable airmass continuing to lift up across much of
central and southern TX given persistent low-level south to
southeast flow in off the western Gulf of Mexico. MLCAPE values
across much of south-central TX in particular are reflective of an
extremely unstable airmass with as much as 4000 J/kg of energy in
place.

As DPVA associated with the shortwave arrives overnight,
convection should develop and expand in coverage, and this will
likely include the northeast advance of a few well-organized
convective clusters (including some supercell activity) that is
seen currently over mainland Mexico west of Laredo.

Recent HRRR guidance has begun to trend wetter across areas of
south-central TX, but the 12Z/18Z HREF model suites in general
favor at least a broken axis of heavy rainfall potential from the
TX Hill Country all the way down through the Lower Rio Grande
Valley going into the overnight period.

PW anomalies are higher (as much as 1.5 standard deviations above
normal) down over the Lower Rio Grande Valley, and this will
contribute to heavy rainfall rates that may reach as high as 2
inches/hour. Some of the more organized and potentially
slow-moving clusters of convection may produce some spotty totals
of 3 to 5 inches through 06Z to 07Z.

This would favor some potential for flash flooding, but with the
coverage of it isolated to widely scattered in nature.

Orrison

....Please see https://urldefense.com/v3/__http://www.wpc.ncep.noaa.gov__;!!=
DZ3fjg!7btvGzvGcSeSXGaTLc2CEuuy7cifOp-MMokFPDBaJZc7GyH532gytoJgJ8RpDch2WMWF=
LBOrWvApVPtwncSsPmziEjY$  for graphic product...

ATTN...WFO...BRO...CRP...EWX...FWD...SJT...

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

LAT...LON   32009940 31659838 30769795 29669777 28289786=20
            27289830 27049925 27619980 28260021 28810051=20
            29210069 29910076 30650068 31430031=20

=3D =3D =3D
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