MESOSCALE PRECIPITATION DISCUSSION 0303
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
932 PM EDT WED AUG 20 2014
 
AREAS AFFECTED...SOUTHERN ND/NORTHEASTERN SD/SOUTHWESTERN MN... 
 
CONCERNING...HEAVY RAINFALL...FLASH FLOODING POSSIBLE 
 
VALID 210132Z - 210602Z
 
SUMMARY...CONVECTION FIRING IN ADVANCE OF A SHORTWAVE SHOULD
CONTINUE TO DROP MODERATE TO HEAVY RAINFALL ACROSS ND. THE
ACTIVITY IS FORECAST TO SPREAD SOUTH AND EAST INTO NORTHEASTERN
SD/SOUTHWESTERN MN WITH FLASH FLOODING POSSIBLE GIVEN HIGH
RAINFALL RATES.

DISCUSSION...A SHORTWAVE MOVING THROUGH WESTERN ND IS LIFTING
ACROSS A REGION OF BROAD UPPER DIFFLUENCE AND ABUNDANT
TROPOSPHERIC MOISTURE. THE 23Z RAP SHOWS THE LLJ INCREASINGLY
MARKEDLY ACROSS THE EASTERN DAKOTAS WITH WIND SPEEDS IN EXCESS OF
35 KNOTS BY 03Z. THE ENHANCED INFLOW WILL TRANSPORT 2 INCH PLUS
PWATS NORTHWARD INVIGORATING ABUNDANT WARM ADVECTION RAINFALL OVER
SOUTHEASTERN ND/NORTHEASTERN SD TONIGHT. THERE APPEARS TO BE
PLENTY OF INSTABILITY INTO THE OVERNIGHT HOURS TO MAINTAIN A
HEALTHY AXIS OF CONVECTION. PROPAGATION VECTORS SUGGEST THE
ACTIVITY SHOULD SLIDE SOUTH OF EAST INTO EASTERN SECTIONS OF THE
DAKOTAS AND EVENTUALLY WESTERN MN. AFTER 06Z THE 850-MB WINDS
BEGIN TO VEER OVER TOWARD THE WEST-SOUTHWEST WHICH SHOULD INCREASE
THE FORWARD PROGRESSION OF THE COMPLEX. OVERALL...FAIRLY CONVINCED
A HEAVY RAINFALL EVENT WILL UNFOLD BUT ONLY MODERATE FFG VALUES
SUGGEST AREAS OF FLASH FLOODING MAY BE MORE LOCALIZED IN NATURE.
HOWEVER...THE 12Z SPC WRF/NSSL WRF...22Z HRRR ARE PRETTY
CONSISTENT IN HIGH PRECIPITATION AMOUNTS ACROSS THE MPD AREA. THE
12Z HRW-ARW AND 12Z HRW-NMM-B ARE NOT AS AGGRESSIVE CARRYING THE
SYSTEM DOWNSTREAM. WILL REASSESS LATER IN THE NIGHT.


RUBIN-OSTER

ATTN...WFO...MPX...FGF...FSD...ABR...BIS...

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

LAT...LON   47570034 47349852 46559703 45889614 45009540 44279587
            43969685 44219767 44959902 45430003 45820119 46840128
            47570034