Subj : MESO: Nws Weather Prediction Center College Park Md
To   : wx-storm@lists.illinois.edu
From : COD Weather Processor
Date : Sat Jun 17 2023 21:27:37

AWUS01 KWNH 172127
FFGMPD
MSZ000-LAZ000-180126-

Mesoscale Precipitation Discussion 0514
NWS Weather Prediction Center College Park MD
527 PM EDT Sat Jun 17 2023

Areas affected...portions of southeastern Louisiana

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

Valid 172126Z - 180126Z

Summary...An intense convective cluster just south of Natchez, MS
may hold together and produce areas of flash flooding - especially
if it can traverse more urbanized areas while producing 2-3
inch/hr rain rates.

Discussion...A right-moving, outflow-dominant supercell was
producing 2-3 inch/hr rain rates (estimated per MRMS) while moving
southward at about 20 mph.  Outflow on the northwestern side of
this supercell was oriented perpendicular to modest
west-southwesterly low-level flow (around 10 knots), which was
allowing for continued upstream convergence and a few additional
showers/thunderstorms to briefly produce heavy rain rates.  The
cell is in an environment characterized by extreme buoyancy (5000
J/kg MLCAPE) and abundant moisture (1.9 inch PW), promoting strong
updrafts and extreme rainfall rates.  The storm was also located
in an area of very high FFG thresholds (exceeding 4 inches/hr),
suggesting that the extreme rain rates would either need to 1)
persist for longer than 1 hour or 2) fall on urbanized/hydrophobic
or low-lying land area to have an appreciable flash flood risk in
the short term.  Modest MRMS Flash responses were noted as the
cell passed south of Natchez earlier, suggesting that the current
flash flood risk is not zero.

Should this cluster hold together on its current path, potential
exists for heavier rain rates to reach the Baton Rouge area and
more populated areas downstream that could result in locally
signficant flash flood potential.  This potential is considered to
be conditional on the cluster retaining it's current intensity,
however.  HRRR forecast soundings downstream of this cell indicate
negligible convective inhibition - only affirming the notion that
this convective cluster could persist over the next couple hours.=20
Isolated, but locally significant flash flood potential exists
with this activity.

Cook

....Please see https://urldefense.com/v3/__http://www.wpc.ncep.noaa.gov__;!!=
DZ3fjg!5RD5SYF9dt_ZbXZALcrumdAKjNxnfWtuI_io7U2ft--aPMSgdr7UKKwegfdS9_wSxfFq=
-8kdfJ5GhxM1oAegLunXrRE$  for graphic product...

ATTN...WFO...JAN...LCH...LIX...

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

LAT...LON   31729118 30898987 30088936 29398940 29239076=20
            30079166 30659183 31569184=20

=3D =3D =3D
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