AWUS01 KWNH 311407
FFGMPD
AZZ000-UTZ000-NVZ000-CAZ000-312005-

Mesoscale Precipitation Discussion 1157
NWS Weather Prediction Center College Park MD
1007 AM EDT Mon Aug 31 2026

Areas affected...portions of Arizona, Utah, and eastern NV

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

Valid 311405Z - 312005Z

Summary...Flash flood potential continues across southern Arizona
in the near term, but will expand northward into much of Utah
through 20Z/2p mountain.

Discussion...A mid-level trough over central California was
continuing to provide forcing/ascent for widespread convection
primarily across eastern AZ and far southern UT this morning. The
greatest concentration of flash flood potential exists across
south-central AZ, where ascent is combining with greater
surface-based instability (1000 J/kg MLCAPE) and very high
moisture content (1.5+ inch PW) for occasional strong storms with
local rain rates exceeding 1 inch/hr at times. These rates were
exceeding FFG on a localized basis, while occasionally occurring
in/near sensitive terrain, prompting continued flash flood
potential in the near term particularly from Phoenix Metro
southward to the International Border.

Recent visible satellite imagery depicts several areas of
cumulus/towering cumulus across areas from western AZ into
south-central NV and western UT, with deeper convection also noted
in south-central UT. That region is also under the influence of
the aforementioned CA mid/upper wave (providing ascent), and as sunshine/destabilization occurs amid the moisture plume over the
area (characterized by 0.75-1.5 inch PW), additional storms with
flash flood potential will likely materialize. Kinematic fields
support appreciable northward/north-northeastward drift of
individual cells, although as convection expands in coverage,
areas of backbuilding and merging will prolong rainfall enough to
promote local 1 inch/hr rain rates and flash flood potential -
especially near sensitive terrain and/or burn scars.

Cook

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

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

LAT...LON 40151162 39211038 37760999 36131023 33781034
32021071 31401106 31521239 32191399 32671469
33721440 34841461 36191496 38761498 39751432
40111312

$$

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