MESOSCALE PRECIPITATION DISCUSSION 0690
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
631 PM EDT THU SEP 22 2016
 
AREAS AFFECTED...EXTREME SOUTHEASTERN NV/WESTERN TO CENTRAL
UT/NORTHWESTERN AZ... 
 
CONCERNING...HEAVY RAINFALL...FLASH FLOODING POSSIBLE 
 
VALID 222230Z - 230230Z
 
SUMMARY...INCREASING COVERAGE OF SHOWERS/THUNDERSTORMS AHEAD OF A
STRONG UPPER TROUGH WILL SUPPORT LOCALIZED HEAVY DOWNPOURS OVER
THE MPD AREA. BEST THREAT FOR FLASH FLOODING WILL BE WITHIN
COMPLEX TERRAIN WHERE RUNOFF ISSUES WOULD BE LIKELY.

DISCUSSION...THE 22Z SURFACE ANALYSIS SHOWED A POTENT COLD FRONT
SWEEPING THROUGH WESTERN UT DOWN TOWARD THE NV/AZ BORDER
ACCOMPANIED BY RATHER MARKED WIND SHIFTS AND TEMPERATURE/DEW
POINTS FALLS. THIS SURFACE BOUNDARY IS MOVING ALONG THE LEADING
EDGE OF A STRONG UPPER LOW MOVING TOWARD THE CENTRAL GREAT BASIN.
IMPRESSIVE MERIDIONAL MOISTURE TRANSPORT IS TAKING SHAPE AHEAD OF
THIS SYSTEM LIFTING DEEP PACIFIC MOISTURE INTO THE REGION. THE
RECENT RAP PWAT ANALYSIS SHOWED 0.75 TO 1 INCH PWATS OVERSPREADING
THE REGION IN THE PRESENCE OF SUFFICIENT INSTABILITY...MLCAPE
VALUES IN THE 500 TO 1000 J/KG RANGE. DYNAMICS ARE QUITE
IMPRESSIVE WITH THIS UPPER TROUGH WITH BROADLY DIFFLUENT UPPER
FLOW AS A 115 KNOT JET STREAK CROSSES UT. ADDITIONALLY...FORECAST
SOUNDINGS SHOW GENERAL UNIDIRECTIONAL SOUTHERLY FLOW WHICH COULD
ALLOW A NORTH/SOUTH LINE TO REMAIN QUASI-STATIONARY AT SOME POINT.

IT WAS DIFFICULT TO FOLLOW ANY INDIVIDUAL HIGH-RESOLUTION MODEL.
THERE IS A DECENT SIGNAL OF MODERATE/HEAVY RAINFALL OVER THE
REGION WHICH WARRANTED AN MPD ISSUANCE. WHILE WIDESPREAD FLASH
FLOODING IS NOT LIKELY...EXPECT SOME ISSUES TO ARISE ON A MORE
LOCALIZED BASIS IN LOCATIONS MORE PRONE TO SUCH INSTANCES.

RUBIN-OSTER

ATTN...WFO...FGZ...PIH...SLC...VEF...

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

LAT...LON   42251273 42051176 41301106 40091063 39121070 
            38161117 37381176 36801254 36541334 36481440 
            38171389 39271326 40551298 41821326