MESOSCALE PRECIPITATION DISCUSSION 0534
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
957 AM EDT TUE AUG 09 2016
 
AREAS AFFECTED...SOUTHERN AZ 
 
CONCERNING...HEAVY RAINFALL...FLASH FLOODING POSSIBLE 
 
VALID 091355Z - 091930Z
 
SUMMARY...VERY INTENSE RAINFALL WITH SLOW-MOVING THUNDERSTORMS
EXPECTED OVER THE NEXT FEW HOURS. 

DISCUSSION...STRONG AND SLOW-MOVING THUNDERSTORMS WITH VERY
INTENSE RAINFALL RATES MAY EXPAND A BIT IN COVERAGE OVER THE NEXT
COUPLE OF HOURS AS DEEP MOISTURE AND A GROWING POOL OF INSTABILITY
BECOMES ESTABLISHED OVER SOUTHERN AZ. COLD-TOPPED CONVECTION HAS
ALREADY BEEN OCCURRING OVER FAR SOUTHWEST COCHISE AND SANTA CRUZ
COUNTIES...AND THIS CLUSTER OF THUNDERSTORMS IS EXPECTED TO DRIFT
WEST AND GRADUALLY EXPAND IN COVERAGE AS STRONG DIURNAL HEATING
ENSUES AND HELPS TO DESTABILIZE THE BOUNDARY LAYER THROUGH MIDDAY.

PWATS OVER SOUTHERN AZ ARE AS HIGH AS 1.75 INCHES AND ARE
CONTINUING TO RISE DUE TO THE NORTHWEST ADVANCE OF TD JAVIER NEAR
THE BAJA PENINSULA. DEEPENING SOUTHERLY FLOW UP ACROSS THE GULF OF
CA AND NORTHWEST MEXICO IS ALLOWING MOISTURE TO BECOME
INCREASINGLY CONCENTRATED...AND THIS WILL RESULT IN VERY HEAVY
RAINFALL RATES THAT MAY APPROACH 2.5 INCHES/HR.

THE HIRES GUIDANCE TENDS TO KEEP THE BULK OF THE CONVECTION
FOCUSED OVER NORTHWEST MEXICO THROUGH EARLY AFTERNOON...BUT BASED
ON THE LATEST SATELLITE AND RADAR TRENDS...SOME OF THIS CONVECTION
SHOULD EXPAND FURTHER OVER SOUTHERN AZ. EXPECT LOCALLY AS MUCH AS
3 TO 4 INCHES OF RAIN WITH ISOLATED HEAVIER AMOUNTS THROUGH THE
VALID TIME PERIOD.

ORRISON

ATTN...WFO...PSR...TWC...

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

LAT...LON   33491180 33361072 32860995 32180968 31620980 
            31301031 31391146 31811258 32481294 33181255