MESOSCALE PRECIPITATION DISCUSSION 0433
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
849 PM EDT WED JUL 11 2018

AREAS AFFECTED...SRN CA

CONCERNING...HEAVY RAINFALL...FLASH FLOODING POSSIBLE

VALID 120048Z - 120248Z

SUMMARY...FLASH FLOODING MAY REMAIN A THREAT FOR A COUPLE OF HOURS
/ THROUGH AT LEAST 02Z / AS OUTFLOWS CONSUME AVAILABLE INSTABILITY
IN THE DESERT AREAS OF SOUTHERN CA.

DISCUSSION...AT 0030Z MULTICELLULAR THUNDERSTORMS HAD PROMPTED A
NUMBER OF FLASH FLOOD WARNINGS IN THE DESERT AREAS OF SOUTHERN CA.
STORMS WERE BEST ORGANIZED IN JOSHUA TREE NATIONAL PARK WHERE
OUTFLOW BOUNDARIES HAD FORMED A COMBINED COLD POOL FROM THE EAST
AND NORTH. OTHER STRONG AND SLOW MOVING CELLS WERE LOCATED TOWARD
THE EAST SIDE OF THE MOUNTAIN RANGES EAST OF SAN DIEGO...HAVING
BEEN PROMPTED BY EARLIER PULSE STORMS AND ASSOCIATED OUTFLOWS.
STILL OTHER CONVECTION WAS OCCASIONALLY PERCOLATING IN EASTERN
RIVERSIDE AND IMPERIAL COUNTIES.

VISIBLE SATELLITE IMAGERY AND THE SPC MESOANALYSIS MIXED-LAYER
CAPE FIELD SUGGESTED THAT THE AREAS OF GREATEST INSTABILITY /
LEAST INHIBITION HAD ALREADY BEEN OVERTURNED...OR WERE BEING
OVERTURNED AT 0030Z. UPDRAFTS MAY BECOME INCREASINGLY SPARSE ALONG
OUTFLOWS AS THEY CONVERGE IN TOWARD THE SALTON SEA WHERE THE SKIES
HAD REMAINED RELATIVELY CLOUD FREE THIS AFTERNOON. THIS IS BORN
OUT SIMULATED REFLECTIVITY FROM THE 21Z HRRR WHICH WAS HANDLING
THINGS WELL AND INDICATES A DIMINISHING TREND AFTER 01Z.

STILL...ANY REMAINING UPDRAFTS...PARTICULARLY THOSE CLUSTERED WEST
OF OCOTILLO...WILL BE CAPABLE OF PRODUCING RAIN RATES EXCEEDING
ONE INCH PER HOUR...WITH VERY MOIST MID AND UPPER LEVEL LAYERS
CONTRIBUTING TO STRONGLY ANOMALOUS PW VALUES 3.0 TO 3.5 STANDARD
DEVIATIONS FROM CLIMATOLOGY...AND MAKING UP FOR A RELATIVE ABSENCE
OF STRONG DEEP LAYER CAPE.

BURKE

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

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

LAT...LON   34381563 34141543 33751529 33371468 33131458
            32881476 32831537 32551553 32161604 32731639
            33081632 33941671 34311647 34231603