MESOSCALE PRECIPITATION DISCUSSION 0664
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
1023 PM EDT THU AUG 10 2017

AREAS AFFECTED...SOUTHEAST CA...AZ

CONCERNING...HEAVY RAINFALL...FLASH FLOODING LIKELY

VALID 110215Z - 110715Z

SUMMARY...ADDITIONAL CLUSTERS OF SLOW-MOVING THUNDERSTORMS WILL
LIKELY GENERATE SOME ADDITIONAL FLASH FLOODING CONCERNS THROUGH
THE EVENING.

DISCUSSION...A WELL-DEFINED LOW TO MID LEVEL MCV OVER THE NORTHERN
GULF OF CA HAS BEEN GREATLY ENHANCING THE MOISTURE TRANSPORT BACK
UP ACROSS MUCH OF THE SOUTHWEST U.S. THIS AFTERNOON AND
EVENING...AND THIS HAS HELPED FACILITATE NUMEROUS CLUSTERS OF
STRONGER THUNDERSTORMS WITH SOME VERY HEAVY RAINFALL RATES THAT
HAVE BEEN OVER 2 INCHES/HR. IN FACT...PWATS ACROSS SOUTHERN AZ
HAVE RISEN TO BACK OVER 2.0 INCHES AND THE LATEST GOES-SOUNDER
DATA SHOWS A POOL OF ENHANCED TROPICAL MOISTURE OVER NORTHWEST MX
AND ADJACENT AREAS OF THE GULF OF CA THAT IS BEING TAPPED.

A FAIRLY BROAD REGION OF LOW LEVEL CYCLONIC FLOW COUPLED WITH A
STILL FAVORABLY UNSTABLE BOUNDARY LAYER AND LOCAL OROGRAPHICS
SHOULD TEND TO MAINTAIN THE CONVECTIVE THREAT THROUGH THE EVENING
HOURS. THE MCV WILL NEED TO BE MONITORED CLOSELY FOR POTENTIALLY
SOME NOCTURNAL CONVECTIVE DEVELOPMENT OVERNIGHT...BUT FOR NOW THE
REMAINING CONVECTION WILL BE TIED INTO THE DIURNAL HEATING FROM
EARLIER IN THE DAY.

EXPECT AS MUCH AS AN ADDITIONAL 2 TO 4 INCHES LOCALLY...AND
ESPECIALLY WITH SLOW CELL MOTIONS. SOME ADDITIONAL FLASH FLOODING
IS LIKELY AS A RESULT...WITH A PARTICULAR FOCUS ON DRY WASHES AND
ARROYOS.

ORRISON

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

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

LAT...LON   36541161 36101078 34271006 33080939 32200900
            31670911 31340977 31391092 31541164 31751228
            31881285 32141373 32551506 32731608 33541632
            34391587 35021512 35381468 35801434 36461284