Mesoscale Precipitation Discussion 0974
NWS Weather Prediction Center College Park MD
421 AM EDT Sat Oct 13 2018

Areas affected...Southern California to Far Western Arizona

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

Valid 130820Z - 131330Z

Summary...The potential for flash flooding over portions of
southern California and far western Arizona desers will persist
into the early morning as moisture moving northward encounters
favorable upper support.

Discussion...Showers and thunderstorms will continue to produce
locally heavy rainfall overnight and into the early morning hours
as moisture deepens over southern California while the upper flow
becomes increasingly difluent aloft.  Precipitable water values
from the 00Z KNKX sounding had already increased to near 1.2
inches while Blended TPW satellite imagery showed that the
moisture in the desert areas were increasing in the mean time as
one area of moisture moved in from the west and as moisture from
the south was being drawn northward by the circulation around the
mid/upper level system.

Rainfall rates approaching 1 inch per hour are expected with
localized amounts exceeding 1.5 inches.

The deep moisture and the upper air support is forecast to
continue to provide support for locally intense rainfall rates
that result in flooding into the early morning.  The greatest
threat will be in, but not limited to, dry washes and burn-scars.

Bann

ATTN...WFO...PSR...SGX...VEF...

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

LAT...LON   34861521 34651427 34191375 33281360 32811406
            32691420 32591442 32541459 32531471 32641477
            32701483 32841576 33251604 33871656 34101732
            34651726 34811662 34851587