MESOSCALE PRECIPITATION DISCUSSION 0145
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
937 PM EDT SAT JUN 21 2014
 
AREAS AFFECTED...ERN SOUTH DAKOTA / SWRN MINNESOTA INTO NERN
NEBRASKA / NWRN IOWA 
 
CONCERNING...HEAVY RAINFALL...FLASH FLOODING POSSIBLE 
 
VALID 220136Z - 220715Z
 
SUMMARY...THE THREAT FOR FLASH FLOODING IS EXPECTED TO INCREASE
OVERNIGHT AS AN ONGOING CONVECTIVE CLUSTER OVER SOUTH DAKOTA MOVES
INTO A REGION OF UNTAPPED INSTABILITY. RAINFALL RATES OF 1 TO 2
IN/HR AND 2 TO 3 IN/3HR ARE EXPECTED THROUGH 07Z.

DISCUSSION...RECENT REGIONAL RADAR TRENDS ACROSS THE CNTRL AND ERN
DAKOTAS HAVE SHOWN AN INCREASE IN COVERAGE OF CONVECTIVE RAINFALL
WITH DUAL POL ESTIMATES OF 1 TO 2 IN/HR FROM KABR WITHIN THE
STRONGEST CORES. IN ADDITION...AN OUTFLOW BOUNDARY WAS OBSERVED
SINKING SWD THROUGH ERN SOUTH DAKOTA AT 115Z WITH REGENERATION OF
CELLS JUST NORTH OF THE BOUNDARY. SURFACE DEWPOINT OBSERVATIONS
FROM 01Z SUGGEST THE GREATEST BOUNDARY LAYER MOISTURE WAS PRESENT
OVER ERN NEBRASKA / WRN IOWA INTO SERN SOUTH DAKOTA ALLOWING
ESTIMATED ML CAPE VALUES OF 2000 - 3000 J/KG PER RECENT SPC
MESOANALYSIS WEBPAGE.

WHILE NOT PARTICULARLY STRONG AT THE MOMENT...SLY LOW LEVEL INFLOW
NEAR 850 MB OF 20 KTS IS EXPECTED TO INCREASE ANOTHER 5 TO 10 KTS
OVER THE NEXT 3 TO 6 HOURS IN ADVANCE OF AN APPROACHING COLD
FRONT. THE SLY FETCH SHOULD CONTINUE TO FEED A MOIST AND UNSTABLE
AIRMASS INTO ERN SOUTH DAKOTA...SUPPORTING THE CONTINUATION OF
CONVECTION WITH A LIKELY ADVANCEMENT TOWARD THE SOUTHEAST PER
CORFIDI VECTORS. THIS IDEA IS MOST SUPPORTED BY RECENT RUNS OF THE
HRRR AND 12Z NSSL WRF WHICH FOCUS THE HEAVIEST RAINFALL THROUGH
12Z IN THE VICINITY OF EXTREME SERN SOUTH DAKOTA. THIS SITUATION
WILL CONTINUE TO BE MONITORED AND UPDATED AS NEEDED...BUT
MEANWHILE...CURRENT FFG OF 1 TO 2 IN/HR COULD BE MET ON A REGIONAL
BASIS ACROSS THE THREAT AREA.

OTTO

ATTN...WFO...MPX...FSD...OAX...ABR...LBF...

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

LAT...LON   45719697 44549567 43499535 42709584 42159683 42309834
            42989916 44269984 44949983 45489930 45829845 45719697