MESOSCALE PRECIPITATION DISCUSSION 0119
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
651 PM EDT SAT JUN 22 2013
 
AREAS AFFECTED...NERN IA...SERN MN INTO WRN WI 
 
CONCERNING...HEAVY RAINFALL...FLASH FLOODING POSSIBLE 
 
VALID 222250Z - 230350Z
 
SUMMARY...CONVECTION IS EXPECTED TO INCREASE THIS EVENING NEAR A
WELL DEFINED FRONTAL BOUNDARY AND POSE AN INCREASED RISK OF FLASH
FLOODING DUE TO ANTECEDENT HEAVY RAINFALL.

DISCUSSION...KMPX RADAR IMAGERY SHOWS SEVERAL CONVECTIVE CELLS
HAVE DEVELOPED WITHIN THE PAST HOUR NEAR A WELL DEFINED STATIONARY
BOUNDARY WHICH EXTENDED WWD ACROSS WISCONSIN INTO A SFC LOW
LOCATED IN SERN MINNESOTA. 22Z RAP MESOANALYSIS INDICATES DIABATIC
HEATING SOUTH OF THE FRONT HAS ALLOWED ML CAPE VALUES TO RISE INTO
THE 2000 - 4000 J/KG RANGE AND CONVECTION APPEARS TO BE TIED TO
WEAK IMPULSE ALOFT MOVING THROUGH NWRN IOWA NOTED ON GOES RGB
AIRMASS SOUNDER IMAGERY. DEEP LOW LEVEL MOISTURE INDICATED BY
SURFACE DEWPOINTS IN THE LOWER 70S COULD SUPPORT ONE HOUR RAINFALL
RATES OF 1-2 IN/HR.

WITH MEAN LAYER FLOW OVER THE REGION FROM THE SOUTHWEST AT 20 - 30
KTS AND SIMILAR LOW LEVEL FLOW OF ROUGHLY THE SAME
MAGNITUDE/DIRECTION... TRAINING CELLS WILL BE POSSIBLE OVER THE
NEXT FEW HOURS AS THESE WIND FIELDS SHOULD REMAIN SIMILAR INTO THE
EARLY OVERNIGHT HOURS PER SHORT TERM RAP GUIDANCE. FLASH FLOOD
GUIDANCE ACROSS SOUTHERN PORTIONS OF THE THREAT REGION IS 1-2 IN /
3 HR DUE IN PART FROM RECENT HEAVY RAINFALL. RECENT RUNS OF THE
HRRR HAVE BEEN CONSISTENT IN EXCEEDING THESE NUMBERS THROUGH 03Z
WITH GENERAL SUPPORT FROM THE 12Z HRW NMM/ARW AND NSSL WRF
ALTHOUGH PLACEMENT DIFFERS A BIT IN THESE MODELS. 

OTTO

ATTN...WFO...GRB...MKX...DVN...ARX...MPX...DMX...

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

LAT...LON   42868869 42608961 42469025 42519096 42699159 43089210
            43379261 43479345 43689377 44029382 44649338 44919234
            45019130 44839021 44548922 43898842 43438830 42868869