Mesoscale Precipitation Discussion 0623
NWS Weather Prediction Center College Park MD
347 AM EDT Fri Aug 10 2018

Areas affected...southern AZ

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

Valid 100746Z - 101145Z

Summary...A threat of flash flooding will continue for another 2-4
hours before convection moves through southern AZ and/or
dissipates.

Discussion...GOES 16 infrared imagery showed convection that was
propagating southwestward from eastern AZ became reinvigorated
over the past 1-2 hours over central AZ. Reported rainfall rates
east of Mesa, AZ in Maricopa county were between 1-1.5 inches in
20-30 minutes ending 0630Z. While the ongoing cluster of storms
over Maricopa and Pinal counties has been moving toward the
southwest at approximately 30 kt, sufficient moisture and
instability remains to produce heavy rainfall rates and possible
flash flooding downstream.

The SPC mesoanalysis from 07Z showed 500-1000+ J/kg MLCAPE just
ahead of the forward propagating cluster of storms with a 10-20
degree surface temperature differential between the cold pool and
locations out ahead of it which should be sufficient to keep the
cluster propagating southwestward into the remaining instability
pool. Continued short term rain rates of 1 to 1.5 inches are
expected to continue for another 2-4 hours at which point the
cluster will have reached the Mexico border and/or weakened in
intensity, ending the flash flood threat across southern AZ.

Otto

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

ATTN...RFC...CBRFC...

LAT...LON   33711323 33521232 33281164 33011114 32691068
            32291067 31771101 31541160 31761245 32251388
            32961411 33481385