Subj : MESO: Nws Weather Prediction Center College Park Md
To   : wx-storm@lists.illinois.edu
From : COD Weather Processor
Date : Sat Jul 22 2023 22:05:27

AWUS01 KWNH 222205
FFGMPD
MSZ000-LAZ000-TXZ000-230230-

Mesoscale Precipitation Discussion 0786
NWS Weather Prediction Center College Park MD
604 PM EDT Sat Jul 22 2023

Areas affected...Far Southeast Texas to Far Southern Mississippi

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

Valid 222203Z - 230230Z

Summary...Thunderstorms this afternoon will be capable of
producing intense rain rates (1-2"/hr) and isolated 2-3" totals
are possible late this afternoon and this evening. This may lead
to localized flash flooding.

Discussion...Thunderstorms have been growing upscale mainly over
southern Louisiana and coastal Mississippi this afternoon along
and south of a quasi-stationary front.  As of 22Z, dewpoints in
the lower to middle 70s combined with air temperatures well into
the 90s in the pre-convective environment south of the front have
yielded sufficient MLCAPE values of 2500+ J/kg. Precipitable water
values are also sufficiently high, analyzed to be between 2" and
2.25" per SPC mesoanalysis and the latest blended TPW product.
Shortwave energy rounding the base of the longwave trough over the
eastern U.S. combined with the moisture and instability has led to
the lines of deepening convection with recent IR imagery showing
rapidly cooling cloud tops.

Recent CAM runs have not been handling the ongoing activity
particularly well along the Gulf coast, particularly with the
developing lines of storms across LA and coastal MS, either being
several hours too late or displaced spatially considerably. The
12Z HREF neighborhood probabilities for 1 inch amounts in 1 hour
increase to more than 50 pct by 00Z with a modest signal for
localized/isolated 2" hourly totals peaking about the same time.=20
Through 03Z, localized 2-4" totals will be possible if cell motion
and the mean-flow aloft align for any length of time.

Over the last 7 days, precipitation has been much below normal in
the outlook area, so any excessive runoff/flooding concerns will
most likely be more isolated in nature and confined to urban
locations and other sensitive/vulnerable spots.

Bann

....Please see https://urldefense.com/v3/__http://www.wpc.ncep.noaa.gov__;!!=
DZ3fjg!75OQzNmiuIY56DrCojOS4d9ugsF5rD2-e6lD_FeQxl1o3sefEIK62smUzrfoOgYmjBZ-=
1frre300lekHDLpSEQ28-AU$  for graphic product...

ATTN...WFO...JAN...LCH...LIX...MOB...SHV...

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

LAT...LON   31579389 31109167 31308988 31298915 31138850=20
            30338864 29908926 29829030 29859159 30199362=20
            30849422=20

=3D =3D =3D
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