MESOSCALE PRECIPITATION DISCUSSION 0276
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
1048 PM EDT FRI AUG 15 2014
 
AREAS AFFECTED...FAR EASTERN MT AND WESTERN ND 
 
CONCERNING...HEAVY RAINFALL...FLASH FLOODING POSSIBLE 
 
VALID 160246Z - 160846Z
 
SUMMARY...A LOW- TO MID-LEVEL CIRCULATION WITHIN WESTERN ND IS
EXPECTED TO INTERACT WITH AN INCOMING OUTFLOW BOUNDARY FROM
NORTHEAST MT AND EVENTUALLY A SQUALL LINE MOVING INTO EASTERN MT. 
FLASH FLOODING IS POSSIBLE OVERNIGHT.

DISCUSSION...THE 02Z OBSERVATIONS REVEAL A WEAK SURFACE
CONVERGENCE ZONE/TROWAL ACROSS THE WESTERN DAKOTAS WITH A WEAK
SURFACE LOW IN WESTERN ND NEAR A SLOW-MOVING LOW- TO MID-LEVEL
CIRCULATION.  PRECIPITABLE WATER VALUES ARE 1.5-1.75" IN THIS
REGION, AND MOST UNSTABLE CAPE VALUES ARE 1000-3000 J/KG.  INFLOW
AT 850 HPA INTO THE AREA -- BEST FROM THE NORTH WHERE INSTABILITY
IS HIGHEST -- IS 20-25 KTS AT THE MOMENT, IMPLYING THAT THE
ENVIRONMENT IS MARGINAL FOR WET MULTICELL STRUCTURES.

AN OUTFLOW BOUNDARY MOVING INTO THE REGION FROM NORTHEAST MT
SHOULD LEAD TO A BRIEF UPTICK IN RAINFALL RATES IN THIS REGION
OVER THE NEXT HOUR OR TWO AS THE LOW- TO MID-LEVEL CIRCULATION
STARTS MOVING EASTWARD.  EVENTUALLY, IN SIX OR SO HOURS, A SQUALL
LINE MOVING ACROSS EASTERN MT WILL MOVE INTO THIS REGION AS WELL,
ENHANCING CONVERGENCE.  WHILE CAPE VALUES ARE EXHAUSTING ACROSS
SOUTHWEST ND, THE REMAINDER OF THE ND AND EASTERN MT IS EXPECTED
TO HAVE AMPLE INSTABILITY OVER THE NEXT SEVERAL HOURS TO SUSTAIN
CONVECTION.  FLASH FLOOD GUIDANCE VALUES ARE QUITE LOW. 
REFLECTING THIS INFORMATION ARE THE 18Z SSEO NEIGHBORHOOD
PROBABILITIES, WHICH ADVERTISE A 50-70% CHANCE OF EXCEEDING THE
THREE HOUR FLASH FLOOD GUIDANCE VALUES OVERNIGHT.   HOURLY
RAINFALL RATES OF 1-2" ARE POSSIBLE CONSIDERING THE AVAILABLE
MOISTURE.  MOST OF THE MESOSCALE QPF GUIDANCE INDICATES A QUICK
2-4" OF RAINFALL IS POSSIBLE HERE, WITH EXREF MEMBER NUMBER 7
ADVERTISING 10" OVER THE NEXT SIX HOURS NEAR THE WESTERN ND/SD
BORDER, WHICH LOOKS QUITE OVERDONE.  FLASH FLOODING IS CONSIDERED
POSSIBLE WITHIN THIS REGION.

ROTH

ATTN...WFO...ABR...BIS...UNR...BYZ...GGW...

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

LAT...LON   46900001 47750039 48310256 47920466 46930515 46000470
            45600358 45590135 46000035 46900001