MESOSCALE PRECIPITATION DISCUSSION 0182
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
1058 PM EDT SAT JUL 27 2013
 
AREAS AFFECTED...NORTHERN AZ...SOUTHEAST UT...SOUTHWEST CO 
 
CONCERNING...HEAVY RAINFALL...FLASH FLOODING LIKELY 
 
VALID 280257Z - 280657Z
 
SUMMARY...AN ORGANIZED AREA OF SHOWERS AND THUNDERSTORMS MOVING
THROUGH NORTHERN AZ AND SOUTHEAST UT OVER THE NEXT SEVERAL HOURS
WILL CAUSE FLASH FLOODING.

DISCUSSION...AN UPPER-LEVEL SHORTWAVE MOVING THROUGH NV HAS LED TO
A SHARP 700 HPA TROUGH STRETCHING ACROSS CENTRAL UT AND NORTHWEST
AZ ALONG WITH ENHANCED UPPER LEVEL DIVERGENCE ACROSS AZ AND
PORTIONS OF UT.  NEAR AND AHEAD OF THE 700 HPA TROUGH, AN
ORGANIZED AREA OF CONVECTION HAS DEVELOPED, WITH BACKBUILDING
NOTED ON RECENT SATELLITE IMAGERY.  PRECIPITABLE WATER VALUES ARE
IN THE 1.25-1.50 INCH RANGE, WHICH IS NEAR THE 85TH PERCENTILE OR
TWO STANDARD DEVIATIONS/SIGMAS ABOVE THE AVERAGE FOR LATE JULY. 
MUCAPE VALUES IN THE REGION ARE AROUND 500 J/KG.  RAINFALL RATES
OF 1-1.5 INCHES PER HOUR HAVE OBSERVED WITH THE ACTIVITY WITHIN
THE U.S. MESONET/MESOWEST NEAR WILLIAMS AZ, WHICH SHOULD BE
REPRESENTATIVE OF CONVECTION WITHIN THIS REGION.  THE 00Z HRRR RUN
ALONG WITH CONVECTIVE TRENDS OVER THE PAST FEW DAYS SUGGEST THAT
THIS ACTIVITY SHOULD CONTINUE GOING FOR 3-4 MORE HOURS BEFORE
WEAKENING AS THE CONVECTION RUNS OUT OF INSTABILITY OVERNIGHT.  A
QUICK 2-4 INCHES OF RAIN IN THIS AREA WILL CAUSE FLASH FLOODING.

ROTH

ATTN...WFO...ABQ...GJT...FGZ...SLC...PSR...VEF...

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

LAT...LON   34591191 34271336 34341481 34641475 35401417 37021316
            38111239 38601138 38660934 38310813 36860889 35541009
            34821127 34591191