MESOSCALE PRECIPITATION DISCUSSION 0221
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
208 PM EDT SAT AUG 24 2013
 
AREAS AFFECTED...SOUTHEAST CA...SOUTHEAST NV...WESTERN
AZ...SOUTHWEST UT 
 
CONCERNING...HEAVY RAINFALL...FLASH FLOODING POSSIBLE 
 
VALID 241800Z - 242100Z
 
SUMMARY...MCS GRADUALLY WEAKENING OVER AZ...BUT ADDITIONAL
CONVECTIVE DEVELOPMENT EXPECTED THROUGH EARLY AFTERNOON.
SLOW-MOVING CLUSTERS OF CONVECTION WITH INTENSE RAINFALL RATES
LIKELY WITH ADDITIONAL FLASH FLOODING POSSIBLE.

DISCUSSION...THE LATEST IR SAT IMAGERY SHOWS A DECAYING MCS OVER W
CNTRL AZ ATTM...WITH A FAIRLY BROAD AREA OF MDT TO LOCALLY HVY
RAINFALL...ESP WITHIN SOME OF THE REMAINING STRONGER CONVECTIVE
CORES. THIS MCS HAS PRODUCED A RATHER WELL-DEFINED COLD POOL WHICH
HAS BEEN FOSTERING ADDITIONAL SLOW-MOVING AND OCCASIONALLY
BACK-BUILDING CONVECTIVE CLUSTERS AROUND ITS WRN FLANK IN FAR WRN
AZ...EXTREME SERN CA AND EXTREME SOUTHERN NV. CONCERN IS THAT THIS
ACTIVITY COULD GROW IN ORGANIZATION OVER THE NEXT COUPLE HOURS AS
STRONGER DIURNAL HEATING HELPS TO DRIVE MDT TO STRONG SFC-BASED
INSTABILITY ADJACENT THE COLD POOL. LATEST RAP ANALYSIS SHOWS A
WELL-DEFINED INSTABILITY AXIS ORIENTED FROM FAR SERN CA NNEWD INTO
EASTERN NV AND CNTRL/WRN UT. LATEST RAP ANALYSIS ALREADY SHOWS IN
EXCESS OF 2000 J/KG OF CAPE LOCALLY AND THIS SHOULD CONTINUE TO
INCREASE.

RAINFALL RATES OF 1.5 TO 2 INCHES/HR ARE EXPECTED...AND COULD BE
LOCALLY HIGHER INVOF OF CELL MERGERS WHICH WAS OF NOTE THIS
MORNING IN CNTRL/WRN AZ. GIVEN THESE RAINFALL RATES...FLASH
FLOODING WILL CONTINUE TO BE POSSIBLE.

ORRISON

ATTN...WFO...FGZ...SLC...PSR...VEF...LKN...

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

LAT...LON   38791166 36671246 35841249 34761190 33551203 32721291
            32761403 33581502 35151582 36911570 38881441 39631276
            38791166