MESOSCALE PRECIPITATION DISCUSSION 0356
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
705 PM EDT MON SEP 08 2014
 
AREAS AFFECTED...SOUTHEASTERN CA/SOUTHERN NV/WESTERN UT/WESTERN
AZ... 
 
CONCERNING...HEAVY RAINFALL...FLASH FLOODING POSSIBLE 
 
VALID 082305Z - 090320Z
 
SUMMARY...ACTIVE CONVECTION CONTINUES TO ERUPT WITHIN A VERY MOIST
THERMODYNAMIC REGIME. DIFFERENTIAL HEATING ZONES BETWEEN REGIONS
OF COLD POOL LADEN AIR AND AREAS OF CLEARING HAVE FUELED
ADDITIONAL THUNDERSTORM ACTIVITY THIS AFTERNOON. EXPECT FLASH
FLOODING TO BE POSSIBLE WITHIN SOME OF THE HEAVIER PRECIPITATION
CORES.

DISCUSSION...IT HAS BEEN A VERY ACTIVE DAY ACROSS THE DESERT
SOUTHWEST WHERE PHOENIX AZ EARLIER REPORTED ITS HIGHEST DAILY
RAINFALL TOTAL FOR ANY CALENDAR DAY. GENERALLY SPEAKING...THE
ATMOSPHERE HAS BEEN OVERTURNED ENOUGH ACROSS CENTRAL AZ THAT THE
MORE ORGANIZED THREAT FOR HEAVY PRECIPITATION HAS ENDED. THE FOCUS
HAS NOW SHIFTED WESTWARD TOWARD THE CA/NV/AZ TRI-STATE BORDER
WHERE DEEP CONVECTION CONTINUES TO FIRE. MUCH OF THE AREA OF
THUNDERSTORM INITIATION IS OCCURRING IN THE PRESENCE OF 2 INCH
PLUS PWATS PER GPS DERIVED VALUES. FOR EARLY SEPTEMBER...MANY OF
THESE NUMBERS HAVE REACHED THE 95TH TO 99TH PERCENTILES. PLENTY OF
INSTABILITY REMAINS ALONG AN AXIS FROM SOUTHEASTERN CA
NORTH-NORTHEASTWARD INTO SOUTHERN NV/SOUTHWESTERN UT. THE 22Z RAP
ANALYSIS SHOWED UP TO 1000 J/KG OF MIXED-LAYER CAPE. EXPECT THE
SLOW-MOVING CLUSTERS OF THUNDERSTORMS TO CONTINUE PRODUCING 1 TO 2
INCH HOURLY RAINFALL RATES GIVEN THE MOIST ENVIRONMENTAL
CONDITIONS. ADDITIONALLY...WARM RAIN PROCESSES HAVE DOMINATED AS
REFLECTED BY THE GENERAL LACK OF LIGHTNING.

IT DOES NOT APPEAR THAT ANY ONE HIGH-RESOLUTION MODEL HAS HANDLED
THE CURRENT ACTIVITY EFFECTIVELY. HOWEVER...THEY ALL DISPLAY SOME
SORT OF ORGANIZED THUNDERSTORM COMPLEX LIFTING THROUGH THE DESERT
SOUTHWEST TOWARD THE SOUTHERN WASATCH. 


RUBIN-OSTER

ATTN...WFO...FGZ...PSR...SGX...SLC...VEF...

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

LAT...LON   39981202 39541125 38631108 37911139 37221194 
            36531267 35901313 35231346 34531379 33631426 
            33441545 33841621 34761652 36451559 37241489 
            37761430 38791342 39761299