Subj : MESO: Nws Weather Prediction Center College Park Md
To   : wx-storm@lists.illinois.edu
From : COD Weather Processor
Date : Sat Jun 17 2023 19:07:40

AWUS01 KWNH 171907
FFGMPD
FLZ000-GAZ000-ALZ000-MSZ000-LAZ000-180105-

Mesoscale Precipitation Discussion 0513
NWS Weather Prediction Center College Park MD
306 PM EDT Sat Jun 17 2023

Areas affected...southern MS/AL into portions of northern FL

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

Valid 171905Z - 180105Z

SUMMARY...Thunderstorms forming in a very unstable environment are
expected to expand and move over a region of the South with
heightened flash flood sensitivity due to recent heavy rainfall
over the past week. Localized to scattered areas of flash flooding
will be possible from the central Gulf Coast into the Florida
Panhandle and northern FL through 01Z.

DISCUSSION...18Z surface observations identified a
quasi-stationary front from the Lower Mississippi Valley into the
northeastern Gulf of Mexico, marked by mid 70s to low 80s surface
dewpoints to its south. Radar imagery placed scattered
thunderstorms in the vicinity of the front from the LA/MS border,
east-southeastward into the FL Panhandle, a region identified by
the 18Z SPC mesoanalysis as having extreme MLCAPE values of 3000
to over 5000 J/kg and PWs of 1.7 to 2.0 inches. Forcing for ascent
appeared to be helped by subtle height falls tied to a mid to
upper level shear axis extending from northern MS into
southeastern GA, gradually sliding southeastward, along with
broadly diffluent flow aloft.

While deeper layer mean winds, Corfidi vectors and right-moving
supercell motions are all expected to fairly progressive toward
the southeast, as storm coverage increases through the remainder
of the afternoon, mergers and areas of short term training with
more organized cells will be possible, resulting in high rainfall
rates that may exceed to 2-3 in/hr. However, eventual congealing
of storms into one or more clusters should favor steady
propagation toward the southeast. Any locations with storms
forming out ahead of forward propagating clusters will be at
increased risk of heavy rain due to repeating rounds. Heavy rain
over parts of the region over the past week have increased
potential for flash flooding such as across southwestern AL where
flash flood guidance values is as low as 1.5 to 2.5 inches per
hour. Localized to scattered areas of flash flooding will be
possible through 01Z.

Otto

....Please see https://urldefense.com/v3/__http://www.wpc.ncep.noaa.gov__;!!=
DZ3fjg!8xWsjWumoodVSxAXdT0uX-Oq7kmTKB6QmMND8AWXMqDeHbI_W_9TDMJ8jXBElJsVLODY=
_Iz6AvjeXjqEgM9K2i5snHU$  for graphic product...

ATTN...WFO...BMX...JAN...JAX...LIX...MOB...TAE...TBW...

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

LAT...LON   32558923 31978763 31558637 30998510 30458327=20
            29948227 29408224 29188242 29078322 29328538=20
            29868785 30338912 30968985 31559037 32069048=20
            32469020=20

=3D =3D =3D
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