Subj : MESO: Nws Weather Prediction Center College Park Md
To   : wx-storm@lists.illinois.edu
From : COD Weather Processor
Date : Tue Aug 26 2025 01:11:09

AWUS01 KWNH 260111
FFGMPD
AZZ000-NVZ000-CAZ000-260600-

Mesoscale Precipitation Discussion 1004
NWS Weather Prediction Center College Park MD
910 PM EDT Mon Aug 25 2025

Areas affected...Southern and Eastern CA...Western and Southern AZ

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

Valid 260110Z - 260600Z

SUMMARY...Additional areas of flash flooding will be likely going
through the evening hours across portions of southern and eastern
CA through western and central AZ.

DISCUSSION...The late-day GOES-W IR satellite imagery shows an
extensive convective cloud canopy over areas of southern and
eastern CA into western and central AZ. Very heavy showers and
thunderstorms continue to locally percolate across the region in
response to localized outflow boundary collisions and some
orographically focused ascent.

Diurnally driven instability continues to be gradually consumed
via the process of convective overturning, but MLCAPE values
remain locally over 1000 J/kg across some of the open desert areas
of eastern CA and also through central AZ with much of this area
so far escaping much of the convective activity.

Recent runs of the experimental WoFS suggest some additional focus
for mesoscale-driven shower and thunderstorm activity across
central AZ in particular which may be aided by close proximity of
some mid-level vort energy lifting northwestward out of the far
northern Gulf of California.

There is also a belt of relatively stronger effective bulk shear
lifting up across southern and central AZ around the western side
of the subtropical ridge off to the east. This shear and the
lingering instability with generally moist deep layer southeast
monsoonal flow will likely support convection lingering well into
the evening.

Rainfall rates will continue to be capable of reaching up to 1.5
inches/hour with the stronger convective cores, with some
additional spotty totals of 2 to 3 inches possible. The 90th
percentile 6-hour QPF from 00Z WoFS supports this over parts of
central and southwest AZ.

This will continue to promote isolated to scattered areas of flash
flooding through this evening before the convection gradually
weakens. Any burn scar locations and the normally dry washes will
continue to be most susceptible to impacts.

Orrison

....Please see https://urldefense.com/v3/__http://www.wpc.ncep.noaa.gov__;!!=
DZ3fjg!9--6CKs_-_lYZCLU7KMZAHifHRWpc2GOFL6JGPBpgoiQTrScsha74K5421HW9LeKLvGB=
wTnDG-GyDAvrDDq_Ybxelho$  for graphic product...

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

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

LAT...LON   36671703 35421529 35601313 35541191 35241105=20
            34731033 33951015 33091063 32361180 32151283=20
            32281408 32571515 33061606 33641703 34921774=20
            36511781=20

=3D =3D =3D
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