MESOSCALE PRECIPITATION DISCUSSION 0318
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
500 AM EDT MON JUN 18 2018

AREAS AFFECTED...WISCONSIN

CONCERNING...HEAVY RAINFALL...FLASH FLOODING POSSIBLE

VALID 180859Z - 181200Z

SUMMARY...LOCALLY HEAVY DOWNPOURS WILL CONTINUE FROM SOUTHWEST WI
EASTWARD ALONG THE AXIS OF BEST MOISTURE FLUX CONVERGENCE THROUGH
12Z BEFORE TAPERING OFF LATER THIS MORNING. 

DISCUSSION...LOCALLY HEAVY RAINFALL FROM STORMS MAY RESULT IN
FLASH FLOODING OVER PORTIONS OF SOUTHEAST MN INTO ADJACENT
PORTIONS OF SOUTHWEST AND CENTRAL WI. 

THE AIRMASS IS LADEN WITH MOISTURE...WITH BLENDED TPW IMAGERY
SHOWING THE STORMS LOCATED IN A REGION OF 2 INCH PRECIPITABLE
WATER VALUES.  THE LOW LEVEL INFLOW WAS ALSO TAPPING THIS AIRMASS.
THE CONVECTION ALSO APPEARED TO BE AIDED BY A WEAK MID LEVEL
SHORTWAVE APPROACHING FROM THE SOUTHWEST. 

WHAT HAS LIMITED THE RAINFALL RATES TO THIS POINT...AND MAY WELL
BE A CONSIDERATION THAT LIMITS WIDESPREAD FLASH FLOOD
POTENTIAL...IS MODEST CAPE IN PLACE.  LATEST SPC MESOSCALE
GUIDANCE SHOWED CAPE VALUES AT OR ONLY MARGINALLY ABOVE 500 J PER
KG IN THE PRECIPITATION AREA. 

OBSERVED RAINFALL RATES HAVE TYPICALLY BEEN AROUND 0.50 INCHES PER
HOUR OR LESS OVERNIGHT...ALTHOUGH SPOTTY AMOUNTS APPROACHING 1.5
INCHES PER HOUR WERE BEING DEPICTED OVER SOUTHWEST WI AHEAD OF THE
WAVE AS EARLY AS 08Z.  THESE AMOUNTS WERE BEGINNING TO APPROACH
FFG VALUES IN AREAS NOT ALREADY SOAKED...AND WOULD RESUKT UB THE
CONTINUATION OF ANY ON-GOING FLOODING FARTHER EAST THROUGH 12Z.

BANN

ATTN...WFO...ARX...GRB...MKX...MPX...

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

LAT...LON   44898939 44718820 44438754 43968765 43878781
            43888895 44008977 43929028 43739082 43849111
            44199109 44469105 44669090 44819066 44879036
            44868988