Mesoscale Precipitation Discussion 0910
NWS Weather Prediction Center College Park MD
920 PM EDT Sun Sep 30 2018

Areas affected...Southern AZ and Southeast CA

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

Valid 010119Z - 010649Z

Summary...Slow moving thunderstorms in a highly efficient
environment may lead to localized flash flooding through the
evening.

Discussion...Most recent mesoanalysis across the area shows SBCAPE
values of around 1500-2000 J/kg with a sharp gradient to less than
500 J/kg across southeast CA. PWATS are very high, running between
1.5 and 1.8" across southern AZ. Aloft, the area is within the
right entrance region of an upper level jet, helping to support
the convection across the area.

There remains a localized near term threat for flash flooding over
the next several hours with some instability expected to persist
across the area through 04-05z. Storms will be capable of hourly
rain rates of around 1"/hr with isolated totals of 1.5" possible,
which would exceed the low FFG across the region. With weak
steering flow, convection will slowly drift northward over the
next several hours with some pockets of training storms possible.

Taylor

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

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

LAT...LON   34551555 34221334 33001107 31251012 31041090
            31151474 31571597 32671637 34071660