MESOSCALE PRECIPITATION DISCUSSION 0396
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
141 AM EDT SAT SEP 27 2014
 
AREAS AFFECTED...EASTERN NV...WESTERN UT...NORTHWEST AZ 
 
CONCERNING...HEAVY RAINFALL...FLASH FLOODING POSSIBLE 
 
VALID 270530Z - 271000Z
 
SUMMARY...CONVECTION SHOULD BECOME MORE ORGANIZED WITH LINEAR
SEGMENTS OVERNIGHT AND A GROWING RISK OF TRAINING CELLS. FLASH
FLOODING WILL BE POSSIBLE THROUGH EARLY MORNING.

DISCUSSION...THE LATEST WV IMAGERY SHOWS A STRONG UPR TROUGH AND
ASSOCD CLOSED LOW MOVING THROUGH CNTRL CA ATTM. DOWNSTREAM FROM
THIS OVER MUCH OF THE GREAT BASIN IS A VERY DIFFLUENT UPR LVL FLOW
REGIME WITH CLEAR TRENDS SEEN TWD STRONGER DEEP LYR FORCING. THE
FORCING ALOFT HAS BEEN INTERACTING WITH A MODEST PLUME OF
INSTABILITY AND MOISTURE ADVECTING NWD OUT OF THE SOUTHWEST...AND
THERE HAS BEEN A TREND OVER THE LAST COUPLE OF HOURS TWD A
SOMEWHAT MORE ORGANIZED MULTICELL CONVECTIVE DEVELOPMENT IN
PARTICULAR OVER FAR SERN NV...EXTREME NWRN AZ AND SWRN UT.

STRONGER DYNAMICS ALOFT WILL BE ARRIVING THROUGH THE OVERNIGHT
HOURS AND DESPITE THE RATHER MODEST INSTABILITY
ENVIRONMENT...STRENGTHENING SHEAR COUPLED WITH AN INCREASE IN THE
AMT OF LOW/MID LVL MOISTURE SHOULD COMPENSATE ENOUGH TO YIELD
SEVERAL ORGANIZED N/S ORIENTED BANDS OF CONVECTION. THE N/S AND
LINEAR MODE OF THE ACTIVITY WILL FAVOR TRAINING CONVECTION.
RAINFALL RATES UP TO 1 INCH/HR ARE EXPECTED AND WITH REPEATING
CELLS...THERE WILL BE A RISK OF FLASH FLOODING...AND ESP OVER
AREAS OF HIGHER TERRAIN.

THE 00Z ARW AND 00Z NMMB APPEAR TO HAVE A REASONABLY GOOD HANDLE
ON THE CURRENT ACTIVITY...AND AGREE VERY WELL THAT CONVECTION WILL
EXPAND IN COVERAGE TO THE NORTH OVER THE NEXT FEW HOURS...WITH
AMTS OF 1 TO 2 INCHES AND ISOLD HEAVIER AMTS POSSIBLE WHERE
TRAINING OCCURS. WILL CONTINUE TO MONITOR.

ATTN...WFO...FGZ...LKN...SLC...VEF...

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

LAT...LON   40201329 39061263 37771242 36421238 35011288 
            34701350 34731404 35291451 35701471 36671486 
            38091496 39311482 40091421