MESOSCALE PRECIPITATION DISCUSSION 0680
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
610 AM EDT SUN AUG 13 2017

AREAS AFFECTED...SOUTH-CENTRAL TO SOUTHEAST AZ

CONCERNING...HEAVY RAINFALL...FLASH FLOODING POSSIBLE

VALID 131010Z - 131315Z

SUMMARY...SHOWER AND THUNDERSTORM ACTIVITY CONTINUES OVER PARTS OF
SOUTH-CENTRAL TO SOUTHEAST AZ. SOME ADDITIONAL FLASH FLOODING IS
POSSIBLE OVER THE NEXT COUPLE OF HOURS...WITH CONDITIONS IMPROVING
TOWARD DAWN.

DISCUSSION...THE LATEST SATELLITE AND RADAR IMAGERY SHOWS
CONVECTION AGAIN PERSISTING OVER AREAS OF SOUTH-CENTRAL AND
SOUTHEAST AZ. THE CONVECTION HAS BEEN GRADUALLY SHIFTING SOUTH
INTO WHERE THERE STILL REMAINS AT LEAST MARGINALLY CONDUCIVE
INSTABILITY...BUT MUCH OF THE ORGANIZATION SEEN OVER THE LAST FEW
HOURS APPEARS TO BE TIED INTO A RATHER DIVERGENT FLOW REGIME ALOFT
COURTESY OF A SHORTWAVE TROUGH FARTHER NORTH THAT IS EJECTING EAST
ACROSS CENTRAL/SOUTHERN UT. IN FACT...THERE HAVE BEEN SOME
OCCASIONAL EFFECTIVE BULK SHEAR VALUES OF NEAR 30 KTS OVER THE
REGION SUPPORTING THE CONVECTION.

BOUNDARY LAYER CINH WILL CONTINUE TO INCREASE...AND THE CONVECTION
SHOULD WEAKEN OVER THE NEXT FEW HOURS. HOWEVER...THERE WILL LIKELY
STILL BE SUFFICIENTLY STRONG ENOUGH CONVECTION...ESPECIALLY OVER
PARTS OF FAR SOUTHEAST AZ FOR SOME ADDITIONAL HEAVY RAINFALL
TOTALS THAT MAY REACH 1 TO 1.5 INCHES. THIS IS CONSISTENT WITH THE
LATEST HRRR GUIDANCE...AND CONSIDERING THESE AMOUNTS...SOME
ADDITIONAL FLASH FLOODING IS POSSIBLE.

ORRISON

ATTN...WFO...EPZ...FGZ...PSR...TWC...

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

LAT...LON   34291218 33801159 32961033 32390939 31800899
            31350950 31301044 31441118 32171212 33661295
            34201277