Subj : MESO: Nws Weather Prediction Center College Park Md
To   : wx-storm@lists.illinois.edu
From : COD Weather Processor
Date : Mon Mar 27 2023 23:06:40

AWUS01 KWNH 272306
FFGMPD
MSZ000-LAZ000-280400-

Mesoscale Precipitation Discussion 0141
NWS Weather Prediction Center College Park MD
705 PM EDT Mon Mar 27 2023

Areas affected...Southern Louisiana

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

Valid 272300Z - 280400Z

Summary...Showers and thunderstorms containing heavy downpours
capable of 1-3"/hr rates may lead to isolated instances of flash
flooding through the evening. The metro area of Baton Rouge will
be particularly vulnerable to these intense rainfall rates, given
urbanized (i.e. relatively hydrophobic) terrain.

Discussion...Deep convective activity has managed to initiate over
southern Louisiana late this afternoon, focused along a sea-breeze
enhanced frontal boundary. The mesoscale environment is
characterized by SB CAPE of 2000-4000 J/kg, precipitable water
values of 1.1-1.4 inches (near the 90th percentile per LIX
sounding climatology), and deep layer (0-6 km) shear of 40-50 kts.
While the 850-300 mb steering flow is about 30-35 kts, the
orientation of the boundary is allowing for some training and
repeating of heavy rainfall, which is supporting localized
rainfall rates in excess of 2"/hr (generally ranging from
1-3"/hr). While 3-hr flash flood guidance is quite high at 3-4",
these repeating rates may still exceed that guidance. The 18z HREF
40-km neighborhood exceedance guidance captures this well,
indicating 20-40% odds of 3"/3-hr exceedance (with the bulls-eye
nearly directly overhead the Baton Rouge metro). Given these
intense rainfall rates, the potential for repeating, and the
proximity to a relatively sensitive metropolitan area, isolated
instances of flash flooding are possible (despite very dry
antecedent conditions, per NASA SPoRT 0-40 cm soil moisture
anomalies in the bottom 10-20th percentile).

Churchill

....Please see https://urldefense.com/v3/__http://www.wpc.ncep.noaa.gov__;!!=
DZ3fjg!-h7-bkzMO_reAOjUIO7e8tC0uReEr6sZAgc3s7WHuiMFXvnAUI1qEZDqda75or-_GGt2=
dDJp_nyZBC5qQchTYX1mRRQ$  for graphic product...

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

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

LAT...LON   31189012 31008944 30479013 30049104 29859222=20
            30029313 30439254 30899133=20

=3D =3D =3D
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