MESOSCALE PRECIPITATION DISCUSSION 0486
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
555 PM EDT SAT JUL 23 2016
 
AREAS AFFECTED...NORTHERN IL...SOUTHEAST WI...EXT EASTERN IA 
 
CONCERNING...HEAVY RAINFALL...FLASH FLOODING LIKELY 
 
VALID 232154Z - 240200Z
 
SUMMARY...STATIONARY EFFICIENT CELLS IN ADVANCE OF APPROACHING
CONVECTIVE COMPLEX IN E IA THAT WILL MERGE/COLLECT AND PRODUCING
FLASH FLOODING CONDITIONS ACROSS N IL THIS EVENING.

DISCUSSION...RADAR/OBSERVATIONS/GOES-E VIS DENOTE A WELL DEFINED
OUTFLOW BOUNDARY LAID OUT BY LEAD WAVE OF CONVECTION ACROSS SE WI.
 CURRENTLY FROM MXO SOUTH OF RFD TO N OF ORD.  VWP AND OBJECTIVE
RAP ANALYSIS INDICATES STRENGTHENING SWLY FLOW ABOVE 850MB WITH
BOUNDARY LAYER SLY FLOW BOTH SUPPORT DEEP MST CONVERGENCE AND
FLUX.   THE ENVIRONMENT ACROSS SE IA/N IL IS HIGHLY UNSTABLE WITH
MLCAPES OVER 5000 J/KG WITH TPWS AOA 2.25" SUPPORTING INCREASING
CONVECTIVE DEVELOPMENT AHEAD OF STRONGEST DPVA FORCING ASSOCIATED
WITH APPROACHING CONVECTIVE COMPLEX IN E IA ATTM.   WITH THE
STRONG SWLY FLOW SUPPORTS UPSTREAM REDEVELOPMENT/BACKBUILDING
ALONG THE OUTFLOW BOUNDARY WITH LIMITED DOWNSTREAM
EVACUATION...SHOULD LEAD TO APPARENT STATIONARY CONVECTION ACROSS
N CENT TO NE IL BEFORE MAIN FORCING APPROACHES FROM THE WEST.
GIVEN THE ENVIRONMENT THIS SHOULD SUPPORT RATES AT OR ABOVE
2"/HR...LIKELY COMPOUNDING TOTALS LIKELY TO EXCEED FFG VALUES
BELOW 2.0"/3HR  
AS FOR THE CONVECTION ALONG THE MAIN UL PVA FORCING...THOUGH IT
HAS BEGUN TO ADVANCE EASTWARD OBSERVED RATES UP TO 2-3"/HR HAVE
BEEN REPORTED...LEADING TO THE POTENTIAL FOR COMPOUNDED TOTALS
ACROSS N IL AFTER 00Z-02Z TIME PERIOD...WITH FF LIKELY...POSSIBLY
AFFECTING HIGH POPULATION CORRIDOR IN CHICAGOLAND AS WELL AS
KENOSHA/RACINE. 

GALLINA

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

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

LAT...LON   43078799 42488730 41858753 41708790 41678962 
            41849076 42159125 42429074 42488992 42698875