MESOSCALE PRECIPITATION DISCUSSION 0399
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
301 PM EDT THU JUL 30 2015
 
AREAS AFFECTED...CENTRAL AND WESTERN AZ 
 
CONCERNING...HEAVY RAINFALL...FLASH FLOODING POSSIBLE 
 
VALID 301855Z - 302355Z
 
SUMMARY...SHOWERS AND THUNDERSTORMS WILL BE DEVELOPING AND
EXPANDING IN COVERAGE OVER THE NEXT FEW HOURS. EXPECT INTENSE
RAINFALL RATES AND POTENTIAL FOR FLASH FLOODING.

DISCUSSION...IR SATELLITE AND RADAR IMAGERY CONFIRMS CONVECTION
INITIATING OVER AND JUST TO THE WEST OF THE MOGOLLON RIM AREA. THE
ACTIVITY IS BEING FOCUSED BY A SMALL SCALE MID LEVEL
CIRCULATION/VORT CENTER WHICH IS WELL DEPICTED IN THE LATEST VIS
SATELLITE IMAGERY.

THE AIRMASS OVER WESTERN AZ IS VERY MOIST WITH GPS-DERIVED PWATS
RUNNING NEAR OR ABOVE 1.5 INCHES...WHICH IS ABOUT 1.5 STANDARD
DEVIATIONS ABOVE NORMAL. OVER THE NEXT FEW HOURS THERE IS EXPECTED
TO BE AN EXPANSION OF CONVECTION DUE TO LOCALLY STRONG DIURNAL
HEATING AND YIELDING SUFFICIENT INSTABILITY IN CONJUNCTION WITH
THE OROGRAPHIC FORCING AND THE AFOREMENTIONED VORT CENTER FOR
CONCENTRATED AREAS OF CONVECTION. GIVEN THE ANOMALOUS MOISTURE
POOLED OVER THE SOUTHWEST AND ESPECIALLY THE DEGREE OF MID AND
HIGH LEVEL MOISTURE AS SEEN IN THE CIRA LAYERED PWAT PRODUCT...THE
SHOWERS AND THUNDERSTORMS SHOULD BE RATHER EFFICIENT RAINFALL
PRODUCERS WITH ENHANCED RATES THAT COULD REACH UP TO 2 INCHES/HR.

THE LATEST HIRES GUIDANCE SUGGESTS SOME CONCENTRATED HEAVY
RAINFALL IMPACTING ESPECIALLY PORTIONS OF WESTERN AND NORTHWEST AZ
THROUGH THE LATE AFTERNOON HOURS. THE 12Z ARW AND 12Z NMMB BOTH
FAVOR 1 TO 2 INCH AMOUNTS WITH ISOLATED HEAVIER TOTALS. GIVEN THE
INTENSE SHORT-TERM RATES AND EFFICIENT NATURE OF THE CELLS...IT IS
POSSIBLE THE HIRES GUIDANCE MAY BE A TAD UNDERDONE WITH THE
RAINFALL POTENTIAL THIS AFTERNOON. FLASH FLOODING WILL BE POSSIBLE
AS THE CONVECTION ORGANIZES AND EXPANDS IN COVERAGE.

ORRISON

ATTN...WFO...FGZ...PSR...VEF...

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

LAT...LON   35631380 35481291 35301222 35141186 34741131 
            34021155 33851261 34111383 34741440 35331430