MESOSCALE PRECIPITATION DISCUSSION 0263
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
341 AM EDT MON AUG 11 2014
 
AREAS AFFECTED...NORTHEASTERN IL/SOUTHEASTERN WI... 
 
CONCERNING...HEAVY RAINFALL...FLASH FLOODING POSSIBLE 
 
VALID 110740Z - 111110Z
 
SUMMARY...WARM ADVECTION PRECIPITATION CONTINUES TO EXPAND IN
COVERAGE ACROSS MUCH OF NORTHERN IL AND INTO SOUTHEASTERN WI. SLOW
CELL MOTIONS COMBINED WITH CELL MERGERS MAY LEAD TO AREAS OF FLASH
FLOODING. THE CONVECTION REMAINS LOW-TOPPED BUT HAS BEEN HIGHLY
EFFICIENT IN RAINFALL PRODUCTION.

DISCUSSION...DURING THE PAST COUPLE OF HOURS...OVERNIGHT
CONVECTION CONTINUES TO BLOSSOM IN THE WARM ADVECTION REGIME. RAP
FORECASTS AND VAD-WIND PROFILES SHOW A RATHER SHARP 850-MB
CONVERGENCE ZONE WHERE MUCH OF THE ACTIVITY HAS FOCUSED IN SSW TO
NNE FASHION. THE LOW-LEVEL SOUTHEASTERLY FLOW HAS ALSO DRAWN IN
HIGHER MOISTURE IN FROM THE UPPER OH VALLEY. INSTABILITY CONTINUES
TO BE RATHER MEAGER WITH MUCAPE VALUES UNDER 500 J/KG ACROSS THE
REGION. IN SPITE OF THE LOW-TOPPED NATURE OF THE CONVECTION...WARM
RAIN PROCESSES HAVE DOMINATED ALLOWING FOR HEFTY RAINFALL RATES
WITHIN THE 1 TO 2 INCH RANGE PER HOUR. THE KLOT DOPPLER RADAR
SHOWED CELL MOTIONS GENERALLY TOWARD THE NORTH WITH REGIONS OF
NORTH/SOUTH TRAINING OBSERVED. HIGH-RESOLUTION GUIDANCE HAS HONED
IN ON THIS REGION WITH FORECAST AMOUNTS OF 1 TO 3 INCHES THROUGH
12Z WITH LOCALLY HIGHER AMOUNTS POSSIBLE. FFG VALUES MAY BE
LOCALLY EXCEEDED...PARTICULARLY NEAR CHICAGO IL AND MILWAUKEE WI.  


RUBIN-OSTER

ATTN...WFO...LOT...ILX...MKX...

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

LAT...LON   43708803 43818741 43608691 43048671 42138687 41568743
            40678800 40828900 41548912 42768860 43708803 
a