Mesoscale Precipitation Discussion 0976
NWS Weather Prediction Center College Park MD
930 AM EDT Sat Oct 13 2018

Areas affected...Eastern California...Southwest Arizona

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

Valid 131329Z - 131929Z

Summary...This is an update to mesoscale precipiation discussion
#0974.  Heavy rain and flash flooding potential will continue into
Saturday morning over eastern California into Southwest Arizona
ahead of the strong closed low off the southern California coast.

Discussion...The latest regional radars and satellite imagery are
showing no let up to the organized area of heavy precipitation
across eastern California into far southwest Arizona ahead of the
strong closed low currently off the southern California coast. 
This closed low is expected to continue its slow eastward push
this morning along the California/Mexico border
region...maintaining strong large scale lift in an axis of PW
values 2.0 to 3+ standard deviations above the mean. 

While the simulated radars from the 0000 utc hi res guidance are
showing some typical biases of being underdone with current
reflectivity...they do show organized activity continuing ahead of
this closed low...possibly re-developing this morning farther to
the southeast over south central Arizona.  This trend seems to
already beginning to occur as per cloud top cooling over far
northern Mexico and far south central Arizona and the
corresponding increase in reflectivity.
 
Rainfall rates of 1 to 1.5"+ per hour likely to continue with the
area of strongest radar returns over far eastern California into
far southwest Arizona.  Hourly rainfall rates from the 0000 utc 
hi res guidance seem a little underdone given current
activity...with rates generally in the .50-1" range.  Rainfall
rates of .50"+ possible farther to the northwest in the more
stratiform region over eastern California.  Rainfall rates likely
will be increasing this morning over south central Arizona as
activity continues to enhance here...with rates of 1"+ per hour
likely.

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

Oravec

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

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

LAT...LON   34961627 34931490 34911380 34841329 34551262
            33981132 33371096 32121097 31461125 31231226
            31621303 32361364 32801409 33101443 33591508
            33931584 34251629 34461671 34751685 34921671