300
AWUS01 KWNH 121521
FFGMPD
AZZ000-UTZ000-NVZ000-CAZ000-122100-

Mesoscale Precipitation Discussion 1023
NWS Weather Prediction Center College Park MD
1120 AM EDT Wed Aug 12 2026

Areas affected...Southern NV...Southwestern UT...Northern AZ

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

Valid 121519Z - 122100Z

SUMMARY...Showers and thunderstorms developing in an anomalously
moist airmass are expected to increase in coverage through the
late morning into the early afternoon hours, with the heaviest and
slower moving storms possibly resulting in some instances of flash
flooding through 21Z.

DISCUSSION...Convection is steadily increasing across northwestern
Arizona late this morning with plenty of monsoonal moisture in
place across the region. PWs are generally on the order of 1.2 to
1.8 inches across western portions of the outlook area from the
latest SPC mesoanalysis, coupled with ample instability given
500-1000 J/kg mixed layer CAPE. This should increase into the
1000-1500 J/kg range later this afternoon, and this should fuel
more widespread convection across much of northern Arizona and
extending into southwestern Utah. There is currently a greater
concentration of storms just to the north of a 850 mb trough
across west-central portions of Arizona.

The current CAM guidance suite is indicating the potential for
patchy QPF maxima of 1-3 inches through 21Z this afternoon, with
the greatest focus likely to be over the northwestern quadrant of
Arizona. Some instances of flash flooding will be possible where
the more persistent and slow moving convection develops,
especially across burn scars, arroyos, or other vulnerable terrain
areas.

Hamrick

...Please see www.wpc.ncep.noaa.gov for graphic product...

ATTN...WFO...FGZ...PSR...SLC...VEF...

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

LAT...LON   38431316 37561249 36701207 35861118 35001017
            33911054 33401190 33381326 33801423 34921454
            36011499 37411490 38281431