MESOSCALE PRECIPITATION DISCUSSION 0349...CORRECTED
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
1101 AM EDT SUN SEP 07 2014
 
CORRECTED FOR TYPOS

AREAS AFFECTED...SOUTHWEST & WESTERN AZ, SOUTHERN CA, SOUTHERN NV 
 
CONCERNING...HEAVY RAINFALL...FLASH FLOODING POSSIBLE 
 
VALID 071457Z - 072057Z
 
SUMMARY...ENHANCED MONSOON CONDITIONS ARE EXPECTED INTO THIS
AFTERNOON DUE TO MUCH ABOVE NORMAL MOISTURE VALUES ACROSS THE
REGION.  RAINFALL RATES UP TO 2" AN HOUR COULD CAUSE FLASH
FLOODING/DEBRIS FLOWS.

DISCUSSION...WIDELY SCATTERED THUNDERSTORMS HAVE DEVELOPED WITHIN
A FIELD OF ASCENDING CUMULI NEAR THE AZ/NV BORDER AND SOUTHERNMOST
CALIFORNIA EARLY THIS MORNING. THE ATMOSPHERE HAS BECOME QUITE
MOIST AS MOISTURE ALOFT FROM TROPICAL STORM NORBERT AND AT
LOW-LEVELS FROM THE GULF OF CALIFORNIA/SEA OF CORTEZ MOVES INTO
SOUTHERN CA.  MORE DISTANT GULF OF MEXICO MOISTURE HAS INFILTRATED
SOUTHERN AZ.  PRECIPITABLE WATER VALUES NEAR 2" EXIST ACROSS
SOUTHERN CA, WHICH ARE NEAR THE 99TH PERCENTILE OR OVER THREE
SIGMAS ABOVE NORMAL FOR EARLY SEPTEMBER.  MIXED LAYER CAPE VALUES
ARE ALREADY >500 J/KG ACROSS WESTERN AZ.  MEAN 850-700 HPA INFLOW
OF 15-20 KTS EXISTS ACROSS THE REGION WHICH SHOULD HELP ORGANIZE
THUNDERSTORM ACTIVITY.

INFLOW ACROSS THE REGION BECOMES MORE SOUTHERLY THIS AFTERNOON
AHEAD OF A DIGGING UPPER LEVEL TROUGH OFFSHORE WESTERN NORTH
AMERICA.  THIS SHOULD CAUSE A RAPID RISE IN MOISTURE ACROSS
SOUTHERN NV DURING THE DAY TODAY.  THIS SHOULD ALLOW CONVECTION TO
MOVE FROM THE TERRAIN OF SOUTHEAST AZ INTO DESERT/VALLEY FLOORS
EARLY ON, BEFORE BECOMING INCREASING CONSTRAINED TO THE TOPOGRAPHY
OF THE MOGOLLON RIM LATER THIS AFTERNOON AFTER EXTENSIVE CLOUD
COVER FROM YESTERDAY'S CONVECTION ERODES. INSTABILITY SHOULD
INCREASE ACROSS THE REGION DUE TO DAYTIME HEATING.  THE BULK OF
THE FLASH FLOOD THREAT APPEARS TO LIE AFTER 18Z, AS INFERRED FROM
THE 00Z AND 06Z SSEO NEIGHBORHOOD PROBABILITIES OF EXCEEDING FLASH
FLOOD GUIDANCE.  DUE TO THE EXISTING MOISTURE, HOURLY RAIN RATES
UP TO 2" AN HOUR ARE POSSIBLE.  THIS TYPE OF RAINFALL COULD LEAD
TO FLASH FLOODING/DEBRIS FLOWS.

ROTH

ATTN...WFO...EPZ...FGZ...LOX...PSR...SGX...SLC...TWC...VEF...

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

LAT...LON   37811433 37621354 37151312 36121307 34851303 
            34041259 33891208 33871132 33341066 32931003 
            32600911 31530904 31340906 31281010 31271108 
            31621217 32171398 32431485 32441485 32621490 
            32621493 32561575 32541654 33171691 33521702 
            33801711 34081711 34261743 34181769 34311796 
            34451822 34481786 34511732 35421634 35851669 
            35931655 35771618 36061601 36421607 36891537 
            37211524