MESOSCALE PRECIPITATION DISCUSSION 0344
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
336 AM EDT THU SEP 04 2014
 
AREAS AFFECTED...SRN WISCONSIN 
 
CONCERNING...HEAVY RAINFALL...FLASH FLOODING POSSIBLE 
 
VALID 040735Z - 041300Z
 
SUMMARY...EXPANDING CONVECTION OVER THE NEXT FEW HOURS WITH
TRAINING OF CELLS FROM ERN IOWA INTO SRN WISCONSIN AND NRN
ILLINOIS IS EXPECTED TO LEAD TO A FLASH FLOOD THREAT. THIS THREAT
IS EXPECTED TO WANE AFTER 13Z WITH WEAKENING OF THE LOW LEVEL JET.

DISCUSSION...REGIONAL RADAR TRENDS OVER THE PAST HOUR HAVE SHOWN
AN UPTICK IN ELEVATED CONVECTION ACROSS SWRN WISCONSIN INTO NWRN
ILLINOIS ON THE COOL SIDE OF A RESIDUAL STATIONARY FRONT DRAPED
NEAR THE MISSOURI RIVER. IT APPEARS THESE STORMS ARE DEVELOPING
WITH THE AID OF LOW LEVEL MOISTURE ADVECTION IN THE 850-700 MB
LAYER WHICH IS OVERCOMING CONVECTIVE INHIBITION DUE TO A WARM
LAYER NEAR 700 MB. GOES SOUNDER TPW SHOWS THE INCREASE IN MOISTURE
NEAR EXPANDING CONVECTION IN SERN IOWA WITH 2+ INCH PWATS. 

850 MB FLOW OF 40 TO 50 KTS FROM THE WSE IS EXPECTED TO PERSIST
FROM ERN IOWA INTO THE THREAT AREA UNTIL ABOUT 12Z AS FORECAST BY
THE RAP...HRRR...HRW-ARW/NMM...AT WHICH POINT THE MAGNITUDE OF
WINDS SHOULD DIMINISH WITH THE DIURNAL CYCLE. GIVEN MEAN STORM
MOTIONS OF 30 KTS TOWARD THE ENE...THE STRONGER LOW LEVEL INFLOW
IS EXPECTED TO ALLOW FOR TRAINING CONVECTION FROM ERN IOWA INTO
SRN WISCONSIN AND NRN ILLINOIS WITH HOURLY RAINFALL RATES OF 1 TO
2 INCHES PER HOUR. TRAINING OF CELLS COULD ALLOW FOR LOCALIZED
TOTALS OF 3-5 INCHES IN A 3 HOUR PERIOD...EXCEEDING FLASH FLOOD
GUIDANCE OF ONLY 2-3 INCHES IN 3 HOURS. 

MODEL SUPPORT IS VARIED AND INCONSISTENT...BUT A COMBINATION OF
THE 00Z HRW-NMM/ARW AND 00Z NSSL WRF APPEAR TO HAVE A DECENT
HANDLE ON THE LOCATION FOR HEAVY RAIN...BUT APPEAR DELAYED BY A
FEW HOURS COMPARED TO CURRENT RADAR. CONFIDENCE IS ONLY MODERATE
GIVEN DIVIDED MODEL SUPPORT. 

OTTO

ATTN...WFO...ARX...DVN...LOT...MKX...

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

LAT...LON   43358973 43188765 41748761 41329035 41049133 
            41449182 42359132