Subj : MESO: Nws Weather Prediction Center College Park Md
To   : wx-storm@lists.illinois.edu
From : COD Weather Processor
Date : Wed May 17 2023 20:27:23

AWUS01 KWNH 172027
FFGMPD
FLZ000-ALZ000-MSZ000-LAZ000-180200-

Mesoscale Precipitation Discussion 0308
NWS Weather Prediction Center College Park MD
426 PM EDT Wed May 17 2023

Areas affected...Southeast LA and MS...Southern and Central
AL...Western FL Panhandle

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

Valid 172025Z - 180200Z

Summary...Rainfall rates of 1-2"/hr may support short-term
localized totals of 3-4". Isolated instances of flash flooding are
possible.

Discussion...A weak low pressure system is providing enhanced
convergence this afternoon for convection, allowing for localized
rainfall rates of 1-2"/hr with relatively slow storm motions. The
mesoscale enviornment within the warm sector is characterized by
surface-based CAPE of 2000-3000 J/kg, precipitable water values of
1.5-1.7 inches (above the 90th percentile, per BMX sounding
climatology), and little to no effective bulk shear (generally
less than 10 kts). This enviornment should continue to support
heavy rainfall (particularly given the anomolous tropospheric
moisture content), but the lack of upper forcing and shear should
keep storm modes rather disorganized (favoring pulse and
multi-cell clusters). Mean flow between 850-300 mb is generally
15-20 kts towards the east, favoring some limited repeating of
1-2"/hr rainfall rates (depsite updraft logevity expected to be
fairly short-lived), and cells closer to the Gulf Coast may
occasionally merge (as the sea breeze provides some northerly
motion to coastal cells). Overall, isolated instances of flash
flooding are considered possible with localized short-term totals
as high as 3-4" (with 3-hr FFGs generally ranging from 2-3").

Churchill

....Please see https://urldefense.com/v3/__http://www.wpc.ncep.noaa.gov__;!!=
DZ3fjg!4gvIWgHI7MeaOym0x9G83kJdDWPhRH2htI47HwZYVbRkkqcJdBwemMMXjg4uCPTYXosR=
F6L7CAHbdVfeBfKvTCTaoHg$  for graphic product...

ATTN...WFO...BMX...HUN...JAN...LIX...MEG...MOB...TAE...

ATTN...RFC...LMRFC...SERFC...NWC...

LAT...LON   34168668 33858551 32228518 31228542 30668591=20
            30358730 30248883 29968984 30279073 31059041=20
            31718960 32258904 34028812=20

=3D =3D =3D
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