MESOSCALE PRECIPITATION DISCUSSION 0476
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
205 PM EDT FRI SEP 04 2015
 
AREAS AFFECTED...NORTHEAST ND...EXTREME NORTHWEST MN 
 
CONCERNING...HEAVY RAINFALL...FLASH FLOODING POSSIBLE 
 
VALID 041805Z - 042205Z
 
SUMMARY...RAPIDLY EXPANDING CLUSTERS OF SHOWERS AND THUNDERSTORMS
MAY PRODUCE SOME LOCALIZED RUNOFF OR FLASH FLOOD PROBLEMS.

DISCUSSION...A WELL-DEFINED SHORTWAVE TROUGH LIFTING
NORTH-NORTHEAST ACROSS SOUTHEASTERN ND EARLY THIS AFTERNOON IS
FOSTERING AN EXPANDING AREA OF HEAVY SHOWERS AND THUNDERSTORMS. IR
SATELLITE IMAGERY SHOWS AND EXPANSION OF INCREASINGLY COLD
CONVECTIVE TOPS...INCLUDING A FEW OVERSHOOTING TOPS...AROUND THE
NORTHERN FLANK OF THE VORT CENTER AND SITUATED IN A GENERAL SW/NE
ORIENTATION JUST AHEAD OF A FRONTAL ZONE AND AN APPROACHING
SURFACE WAVE.

DESPITE A RELATIVELY STABLE BOUNDARY LAYER WHICH IS RESULTING IN A
BIT OF LOWER LEVEL CINH...THE CONVECTION IS ORGANIZING IN AN
ELEVATED FASHION WITH THE AID OF A MODERATELY INSTABILITY
CHARACTERIZED BY 2500 TO 3000 J/KG OF MUCAPE AND A RELATIVELY
MOIST ENVIRONMENT WITH GPS-DERIVED PWATS LOCALLY EXCEEDING 1.5
INCHES. THE STRONGER DYNAMICS ALOFT WITH THE APPROACHING SHORTWAVE
AND LOW LEVEL FORCING NEAR THE FRONT ARE SUFFICIENT TO OVERCOME
THE OTHERWISE UNFAVORABLE LOWER LEVEL CINH.

THE 12Z ARW AND 12Z NMMB BOTH APPEAR TO HAVE A REASONABLY GOOD
HANDLE ON THE CURRENT CONVECTIVE ACTIVITY...AND THESE MODELS
SUPPORT SOME LOCALIZED 2 TO 4 INCH RAINFALL TOTALS THROUGH THE
AFTERNOON AS THE ENERGY LIFTS THROUGH NORTHEAST ND. GIVEN THE
EXPECTED SHORT-TERM RAINFALL RATES OF 1 TO 2 INCHES/HR ARE
EXPECTED...AND SOME LOCALIZED TRAINING AND/OR CELL-MERGER
THREAT...THERE MAY BE SOME LOCALIZED POTENTIAL FOR RUNOFF PROBLEMS
AND FLASH FLOODING.

ORRISON

ATTN...WFO...BIS...FGF...

ATTN...RFC...MBRFC...NCRFC...

LAT...LON   49399748 49219654 48639663 47879765 47599844 
            47649909 47879938 48259924 48999833