969
AWUS01 KWNH 131748
FFGMPD
AZZ000-UTZ000-132300-

Mesoscale Precipitation Discussion 1274
NWS Weather Prediction Center College Park MD
141 PM EDT Sun Sep 13 2026

Areas affected...Southern UT...Central AZ

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

Valid 131741Z - 132300Z

SUMMARY...Slow moving showers and thunderstorms are beginning to
increase in coverage and intensity across the outlook area. Some
instances of flash flooding will be possible through the
mid-afternoon hours, particularly across vulnerable locations.

DISCUSSION...Regional Doppler radars and GOES-W visible satellite
imagery are indicating convective initiation across western
portions of the Mongollon Rim. Daytime heating is adding to an
already most and unstable boundary layer, characterized by PWs on
the order of 1 to 1.8 inches and mixed layer CAPE of 1000-1500
J/kg based on the latest SPC mesoanalysis. In addition, surface to
300 mb flow is very weak as evident from the 12Z Phoenix sounding,
and this will result in slow cell motions and therefore enhanced
rainfall rates where these cells develop.

The latest CAM guidance suite agrees well on the general placement
of most concentrated thunderstorm activity across far southern
Utah into north-central Arizona, but differ more on overall
magnitude of the QPF maxima. The RRFS is generally heavier with
the strongest storms, generally up to 2 inches in some instances,
whereas the HRRR is generally under an inch with those same
storms. Areas that have received heavy rainfall over the past 24
hours, along with recent burn scars and dry canyons, will be most
susceptible to potential flooding through 23Z.

Hamrick

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

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

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

LAT...LON   38091193 37791065 36311046 34371033 33171001
            31960999 31311007 31341107 31591182 31971297
            32791320 33691323 35051380 36481369 37601313