MESOSCALE PRECIPITATION DISCUSSION 0249
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
917 PM EDT SUN AUG 03 2014
 
AREAS AFFECTED...PORTIONS OF THE DESERT SOUTHWEST 
 
CONCERNING...HEAVY RAINFALL...FLASH FLOODING LIKELY 
 
VALID 040117Z - 040417Z
 
SUMMARY...THUNDERSTORMS WITH VERY HEAVY RAIN ARE EXPECTED TO
CONTINUE UNTIL ~04Z BEFORE DECREASING IN COVERAGE AND INTENSITY. 
UNTIL THEN, FLASH FLOODING/DEBRIS FLOWS ARE LIKELY IN THIS AREA.

DISCUSSION...AN UPPER LEVEL LOW MOVING INTO CA HAS LED TO A
SIGNIFICANT FLASH FLOOD EVENT ACROSS SOUTHERN CA AND PORTIONS OF
WESTERN AZ, WITH HOURLY RAIN RATES OF 3-4" REPORTED -- SIMILAR TO
THEIR ANNUAL AVERAGE RAINFALL.  INFLOW AT 700 HPA CONTINUES TO BE
IN THE RANGE OF 15-20 KTS ACROSS AZ PER VAD WIND PROFILES, WHICH
IS HELPING TO ORGANIZE ACTIVITY IN WESTERN AZ.  PER THE SPC
MESOANALYSIS, FAR SOUTHERN NV, SOUTHEAST CA, WESTERN AZ, AND THE
WESTERN UT/AZ BORDER CONTINUE TO HAVE MIXED LAYER CAPES AT OR
ABOVE 1000 J/KG, WITH A POCKET ABOVE 1500 J/KG NEAR THE AZ/NV/CA
BORDER.

THE 18Z SSEO PROBABILITIES OF EXCEEDING FLASH FLOOD GUIDANCE
SLOWLY DROP OFF THROUGH 04Z ACROSS THIS REGION, WHICH IS EXPECTED
TO BE WHEN THE CAPE VALUES FADE REGION-WIDE.  UNTIL THEN, HOURLY
RAIN RATES UP TO 2-3" CANNOT BE RULED OUT, WITH LOCAL MAXIMA OF
3-4" POSSIBLE WHERE CELLS TRAIN AND/OR MERGE.  FLASH FLOODING IS
CONSIDERED LIKELY IN THIS REGION UNTIL ABOUT 04Z.

ROTH

ATTN...WFO...FGZ...SLC...PSR...VEF...SGX...REV...HNX...LOX...

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

LAT...LON   37561473 37651343 37891261 37591212 36601157 35361117
            34391138 33241172 33171238 33451367 33731461 33511597
            33821645 33591641 33461709 33651766 33851772 33931777
            34001748 34091763 34031775 34291838 34531864 34571942
            34841978 35181886 35781885 36741895 37331915 37391861
            37151821 37981845 37491739 37581550 37561473