MESOSCALE PRECIPITATION DISCUSSION 0592
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
731 PM EDT MON AUG 22 2016
 
AREAS AFFECTED...SOUTHWEST UT...NORTHWEST AZ 
 
CONCERNING...HEAVY RAINFALL...FLASH FLOODING POSSIBLE 
 
VALID 222330Z - 230300Z
 
SUMMARY...SLOW-MOVING CLUSTERS OF THUNDERSTORMS WILL PERSIST OVER
THE NEXT FEW HOURS. HEAVY SHORT-TERM RAINFALL WILL RESULT IN SOME
RUNOFF AND POSSIBLE FLASH FLOODING.

DISCUSSION...GOES-14 1-MINUTE VISIBLE IMAGERY CONFIRMS AN
EXPANSIVE AREA OF UNSTABLE AIR OVER NORTHWEST AZ AND SOUTHWEST
UT...WITH WIDESPREAD CU/TCU COVERAGE. NUMEROUS SHOWERS AND
THUNDERSTORMS HAVE BEEN DEVELOPING WITH AID OF A BROAD MID LEVEL
LOW CIRCULATION OVER SOUTHERN NV. A 2032Z AQUA-MODIS PASS CONFIRMS
PRESENCE OF AN ELONGATED AXIS OF MID LEVEL SHORTWAVE ENERGY THAT
INVOLVES SOUTHERN NV AND EXTENDS EAST ACROSS CENTRAL/NORTHERN AZ.

THE UPPER FLOW OVER THE REGION IS BROADLY DIFFLUENT GIVEN THE
UPPER SUPPORT...AND COUPLED WITH AS MUCH AS 1000 TO 1500 J/KG OF
MLCAPE...AND PWATS LOCALLY NEAR 1.25 INCHES...CONVECTION HAS BEEN
ALLOWED TO EXPAND IN COVERAGE OVER THE LAST COUPLE OF HOURS.

SOME OF THE COLDEST CLOUD TOPS VIA GOES-14 SRSOR IR DATA OVER THE
LAST 15 TO 30 MINUTES HAS BEEN NOTED OVER SOUTHWEST UT...AND
SUGGESTIVE OF STRONGER FORCING/ASCENT. THERE WILL BE A CONCERN
OVER THE NEXT 2 TO 3 HOURS ACROSS ESPECIALLY THE HIGHER TERRAIN OF
SOUTHWEST UT AND PARTS OF NORTHWEST AZ FOR HEAVY RAINFALL RATES OF
1 TO 1.5 INCHES/HR. THESE RATES MAY LEAD TO ENHANCED POTENTIAL FOR
FLASH FLOODING AND ESPECIALLY FOR ADJACENT VALLEYS AND AREA DRY
WASHES WHERE WATER MAY BE CHANNELED RAPIDLY AND EFFICIENTLY
DOWNSTREAM.

CONDITIONS WILL IMPROVE LATER THIS EVENING AS INSTABILITY BEGINS
TO WANE...BUT EXPECT SHORT-TERM RAINFALL TOTALS OF AS MUCH AS 2 TO
4 INCHES GIVEN THE HEAVY RATES AND SLOW CELL MOTION. THUS...THE
POTENTIAL FOR RUNOFF/FLASH FLOOD CONCERNS CONTINUES.

ORRISON

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

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

LAT...LON   37821182 37251159 36391223 35411253 34771249 
            33951210 33681278 33931363 34351413 34991439 
            35951432 37121383 37691301