Subj : MESO: Nws Weather Prediction Center College Park Md
To   : wx-storm@lists.illinois.edu
From : COD Weather Processor
Date : Sat Aug 19 2023 17:25:55

AWUS01 KWNH 191725
FFGMPD
AZZ000-CAZ000-192323-

Mesoscale Precipitation Discussion 0947
NWS Weather Prediction Center College Park MD
125 PM EDT Sat Aug 19 2023

Areas affected...southeastern California, western Arizona

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

Valid 191723Z - 192323Z

Summary...A lingering, yet isolated flash flood risk continues
across the Lower Colorado River Valley and areas east of the
Peninsular Ranges through 23Z.

Discussion...Deep, vigorous convection earlier across the
discussion area resulted in a few areas of 1-2.5 inch/hr rain
rates (estimated per MRMS) along with at least one report of
debris flow and a road closure this morning.  Since that time,
widespread convective overturning has stabilized the airmass
somewhat across the discussion area, with the strongest
instability (coincident with deeper convection) residing just
south of the international border.  This has resulted in more
widespread stratiform precipitation with embedded convective
elements that have locally enhanced rain rates.  A few spots of
1-1.5 inch/3-hr rainfall rates have been estimated per MRMS across
portions of Imperial and Riverside Counties, and the flash flood
threat appears to be maximized there in the short term.

Through the afternoon, continued upper level difluence/divergence
will support areas of rainfall across the discussion area.=20
Additionally, where better surface-based instability can
materialize from 1) the northern Gulf of California (where 70s F
dewpoints were supporting 1500+ J/kg SBCAPE) and/or 2) amid areas
of surface heating that can allow for airmass recovery on the
periphery of the expansive rain shield, a better chance for deep
convection and flash flood potential should materialize.  On the
whole, the short term flash flood threat should remain isolated at
best over the next 2-3 hours before perhaps increasing again=20
where destabilization can occur after 19Z or so.

Cook

....Please see https://urldefense.com/v3/__http://www.wpc.ncep.noaa.gov__;!!=
DZ3fjg!99o0OjwgYTaK_OAGVXcdHoiGWmBKMhlh-5J6HEqpNHpfOoe-4WXbO1ps1Z5ZtqNejfdS=
V7qLPrRRihay5-jeH_07G34$  for graphic product...

ATTN...WFO...FGZ...PSR...SGX...TWC...VEF...

ATTN...RFC...CBRFC...CNRFC...NWC...

LAT...LON   34881478 34821373 34461268 33601239 32651296=20
            32121405 32461582 32711625 33451648 34311668=20
            34761610=20

=3D =3D =3D
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