MESOSCALE PRECIPITATION DISCUSSION 0278
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
442 AM EDT SAT AUG 16 2014
 
AREAS AFFECTED...PORTIONS OF ND AND NORTHERN SD 
 
CONCERNING...HEAVY RAINFALL...FLASH FLOODING POSSIBLE 
 
VALID 160841Z - 161401Z
 
SUMMARY...A SLOW-MOVING AREA OF THUNDERSTORMS WITH HOURLY RAIN
RATES UP TO 2" IS EXPECTED TO PERSIST INTO THE MORNING.  FLASH
FLOODING REMAINS POSSIBLE.

DISCUSSION...A LOW- TO MID-LEVEL CIRCULATION HAS BEEN MOVING
EASTWARD ACROSS ND AT 5-10 KTS -- SIMILAR TO WHAT IS INDICATED BY
BOTH SETS OF PROPAGATION VECTORS -- ACCOMPANIED BY THUNDERSTORMS
WITH COLD CLOUD TOPS AND HEAVY RAINFALL.  PURE RADAR ESTIMATES OF
STORM TOTAL RAINFALL HAVE APPROACHED 12" IN A COUPLE SPOTS ACROSS
ND.  HOWEVER, A FEW RAINFALL REPORTS RELAYED BY THE BISMARCK ND
FORECAST OFFICE OVERNIGHT INDICATE THAT RADAR ESTIMATES COULD BE A
BIT HIGH, LOWERING ESTIMATES OF THE POSSIBLE EXTREMES TOWARD 8". 
PRECIPITABLE WATER VALUES REMAIN AROUND 1.75", NEAR THE 99TH
PERCENTILE FOR MID-AUGUST.  NEARBY MUCAPE VALUES ARE 500-1000
J/KG.  INFLOW AT 850 HPA IS ROUGHLY 20-25 KTS FROM THE
NORTH-NORTHWEST INTO THE THUNDERSTORM AREA.  THESE PARAMETERS JUST
MEET THE THRESHOLD FOR THE WET MULTICELL ENVIRONMENT.

COLLABORATION WITH SAB/NESDIS SUGGESTS THIS THUNDERSTORM AREA
SHOULD PERSIST UNTIL SUNRISE. CONVERGENCE AT 850 HPA NOTED IN
REGIONAL VAD WIND PROFILES AROUND NORTHERN SD CONTINUES TO SUPPORT
EXTENDING THE RISK INTO THAT REGION. THE 18Z/00Z SSEO NEIGHBORHOOD
PROBABILITIES OF EXCEEDING FLASH FLOOD GUIDANCE IN THREE HOURS
ADVERTISE THAT AREAS AROUND SOUTH-CENTRAL ND HAVE A >50% OF
EXCEEDING GUIDANCE UNTIL 14Z.  THE SYSTEM IS MOVING INTO AN AREA
WITH HIGHER MUCAPE, WHICH ALSO SUGGESTS THE STORMS COULD MAINTAIN
THEMSELVES FOR A WHILE LONGER.  HOURLY RAIN RATES UP TO 2" AN
HOUR, WITH LOCAL AMOUNTS OF 2-4" SEEN WITHIN THE AVAILABLE
MESOSCALE QPF GUIDANCE IN THIS REGION, ARE EXPECTED.  FLASH
FLOODING REMAINS POSSIBLE CONSIDERING THE RELATIVELY LOW FLASH
FLOOD GUIDANCE. 

ROTH

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

LAT...LON   47619988 48150095 48150233 47770269 46910231 45910142
            45480084 45480037 45799963 46229939 46879948 47619988