Subj : MESO: Nws Weather Prediction Center College Park Md
To   : wx-storm@lists.illinois.edu
From : COD Weather Processor
Date : Sun Aug 24 2025 19:04:49

AWUS01 KWNH 241904
FFGMPD
AZZ000-UTZ000-NVZ000-250103-

Mesoscale Precipitation Discussion 0992
NWS Weather Prediction Center College Park MD
304 PM EDT Sun Aug 24 2025

Areas affected...northwestern Arizona, southern Utah, and
southeastern Nevada

Concerning...Heavy rainfall...Flash flooding likely

Valid 241903Z - 250103Z

Summary...Scattered thunderstorms are quickly expanding in
coverage across the Colorado River Valley and vicinity.  The
storms are in a favorable environment for localized rain rates
exceeding 1 inch per hour.  Flash flooding is likely - especially
in terrain-favored areas and near burn scars.

Discussion...Recent satellite/lightning data indicates a distinct
increase in convective activity across terrain-favored ridgelines
in northwestern Arizona and south-central Utah over the past hour.
 The storms are forming in response to 1) strong
insolation/destabilization across the area, with MLCAPE values
exceeding 1000 J/kg, 2) anomalously high moisture content (PW
values as high as 1.4 inch), and 3) very subtle mid-level
vorticity maxima rotating northward along the western periphery of
a stout mid/upper ridge near the Four Corners region.  Wind fields
aloft were strong enough to favor slow northward storm motions
(around 10-15 knots).  Despite these storm motions, localized
backbuilding (evident per radar/MRMS) and overall convective
intensity has still supported local instances of rain rates
reaching 1 inch/hr at times.

These rain rates should occur across locally sensitive ground
conditions resulting from several burn scars.  Slot canyons in
southern Utah and vicinity area also at risk of locally heavy rain
rates.  As convection continues to mature and expand in coverage,
several instances of flash flooding are expected.

Most of the convection should be diurnally driven, with model
guidance suggestive of flash flood potential existing through at
least 01Z/7p MDT.

Cook

....Please see https://urldefense.com/v3/__http://www.wpc.ncep.noaa.gov__;!!=
DZ3fjg!4wTGC0DCHOW0D4pa35mAoBzjW8mKtcs0Th9B2gQwnpoNKsxWRuOw_12vfU808w1DB7Bn=
yG5SPS2Y4ZHnRRycX2nSfXw$  for graphic product...

ATTN...WFO...FGZ...GJT...LKN...SLC...VEF...

ATTN...RFC...RSA...STR...NWC...

LAT...LON   39581229 39111117 37681086 37011072 35701114=20
            34911127 34151232 34631405 35071456 36321543=20
            37901527 39131400=20

=3D =3D =3D
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