MESOSCALE PRECIPITATION DISCUSSION 0400
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
925 PM EDT FRI JUL 31 2015
 
AREAS AFFECTED...AZ 
 
CONCERNING...HEAVY RAINFALL...FLASH FLOODING POSSIBLE 
 
VALID 010120Z - 010600Z
 
SUMMARY...NUMEROUS SHOWERS AND THUNDERSTORMS WILL CONTINUE THROUGH
THE LATE EVENING HOURS. SLOW-MOVING CELLS AND INTENSE RAINFALL
RATES WILL PROMOTE THE POTENTIAL FOR FLASH FLOODING OVER THE NEXT
FEW HOURS.

DISCUSSION...THE LATE-DAY GOES-RGB IMAGERY SUGGESTS A WEAK MID
LEVEL CIRCULATION MOVING NORTHWEST OUT OF NORTHWEST MEXICO AND
INTO SOUTHERN AZ AT THIS TIME. THIS CIRCULATION IS ACCOMPANIED BY
A POOL OF DEEPER MOISTURE AS DEPICTED BY GPS-DERIVED PWATS AND THE
LAYERED PWAT PRODUCT WHICH SHOWS ELEVATED MID AND HIGH LEVEL
MOISTURE ADVANCING NORTHWEST. SUFFICIENT FORCING WITH THE
CIRCULATION AND FAVORABLE THERMODYNAMICS HAS ALREADY BEEN YIELDING
NUMEROUS CLUSTERS OF HEAVY SHOWERS AND THUNDERSTORMS THROUGH LATE
AFTERNOON...BUT WITH THE INCREASE IN MOISTURE TRANSPORT...RAINFALL
RATES SHOULD TEND TO INCREASE THROUGH THE EVENING HOURS. THE
CONVECTION HAS BEEN RATHER SLOW MOVING AND THIS HAS BEEN YIELDING
LOCALLY VERY HEAVY RAINFALL...WITH RATES OF UP TO 1.5 INCHES/HR AS
PER DUAL-POL ESTIMATES.

OVER THE NEXT FEW HOURS...THE LATEST HRRR SUGGESTS ADDITIONAL
FOCUS FOR HEAVY SHOWERS AND THUNDERSTORMS GIVEN THE DEEPENING
MOISTURE PROFILES AND SUFFICIENT INSTABILITY/FORCING IN VICINITY
OF THE MID LEVEL VORT CENTER. EXPECT AT LEAST SOME POTENTIAL FOR
FLASH FLOODING...ESPECIALLY IN VICINITY OF ARROYOS WHERE THE
INTENSE RATES AND SLOW MOVEMENT WILL FAVOR RAPID RUNOFF. WILL
CONTINUE TO MONITOR.

ORRISON

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

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

LAT...LON   36461219 36021099 35151021 33720964 31610947 
            31091012 31181143 31791236 32281288 33061335 
            33751370 34571401 35691399 36251355