643 

AWUS01 KWNH 232334

FFGMPD

AZZ000-240515-



Mesoscale Precipitation Discussion 1118

NWS Weather Prediction Center College Park MD

734 PM EDT Sun Aug 23 2026



Areas affected...south-central to southern AZ



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



Valid 232333Z - 240515Z



Summary...Flash flooding will be possible across portions of

southern AZ through 05Z with at least isolated coverage. High

sub-hourly rain rates, locally exceeding 1 inch in 15 minutes, are

expected to lead to 1 to 2 inch totals (locally higher possible).



Discussion...Satellite and radar imagery showed a few ongoing

thunderstorms across the higher terrain of southeastern AZ as of

23Z with a general movement toward the west, though some cell

motions were slower than others. Additional attempts at convective

development were also noted over southern Maricopa/Pinal counties

in visible imagery while outflow was propagating southward off of

the Mogollon Rim across northern Maricopa County. The recent

increase in cell coverage has begun to form a couple of outflow

generated cold pools over southeastern AZ, with the potential

early stages of congealing occurring. Blended TPW imagery has

shown increasing moisture from the Gulf of CA into portions of

south-central and southwestern AZ since 12Z with values of 1.1 to

1.7 inches as of 22Z, helping contribute to MLCAPE of 500 to 2000

J/kg (highest over southwestern AZ as seen on the 23Z SPC

mesoanalysis).



Given the center of the mid to upper-level ridge was over

southeastern NM, an increased southerly trajectory to the low to

mid-level flow was seen into southern AZ. Expectations are for

continued convective development over the next couple of hours

over southeastern AZ (and possibly out ahead over south-central AZ

near/ahead of outflow), with movement around the ridge toward the

west and northwest. There is some uncertainty regarding convective

development over parts of southwestern AZ given increasing values

of convective inhibition with western extent as noted on SPC

mesoanalyses (Yuma County) but lift associated with outflow

propagation should be enough to overcome weaker values of

inhibition farther east (Pima and southern portions of Maricopa

and Pinal counties) if organization continues to increase. Should

at least a weakly organized convective cluster form, system

propagation should limit the duration of rainfall over any given

location. However, the environment will be supportive of high

sub-hourly rain rates similar to what has already been observed in

northern Santa Cruz County just after 22Z (1.38 inches in 15

minutes). 0.5 to 1.0+ inches in 15 minutes will be possible with

an evolution toward the west and northwest with time through 05Z,

possibly resulting in flash flooding of low water crossings,

normally dry washes and low lying areas.



Otto



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



ATTN...WFO...PSR...TWC...



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



LAT...LON   33791258 33641153 32471025 31700998 31201023 

            31561222 32091343 32761371 33151371 33671330