672
AWUS01 KWNH 111520
FFGMPD
OHZ000-MIZ000-INZ000-WIZ000-ILZ000-112000-
MESOSCALE PRECIPITATION DISCUSSION 1008
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
1117 AM EDT TUE AUG 11 2026
AREAS AFFECTED...SOUTHERN WI...NORTHERN IL...NORTHERN
IN...SOUTHERN MI...NORTHWESTERN OH
CONCERNING...HEAVY RAINFALL...FLASH FLOODING POSSIBLE
VALID 111517Z - 112000Z
SUMMARY...AN MCS TRACKING ACROSS NORTHERN ILLINOIS LATE THIS
MORNING WILL SUPPORT THE DEVELOPMENT OF ADDITIONAL CONVECTION WITH
HIGH RAINFALL RATES THROUGH 19Z ACROSS THE OUTLOOK AREA. SOME
INSTANCES OF FLASH FLOODING WILL BE POSSIBLE WITH THE MOST
PERISTENT THUNDERSTORM ACTIVITY.
DISCUSSION...REGIONAL DOPPLER RADARS SHOW A LONG LIVED MCS
CURRENTLY TRACKING ACROSS NORTHERN ILLINOIS TOWARDS THE GREATER
CHICAGO METRO AREA. MEANWHILE, A SEPARATE COMPLEX OF STORMS HAS
RAPIDLY INCREASED IN COVERAGE AND INTENSITY ACROSS NORTHWESTERN
INDIANA, AND RECENT RADAR SCANS ARE INDICATING THESE SEPARATE
COMPLEXES ARE STARTING TO CONGEAL INTO A SINGLE LARGER COMPLEX.
THIS IS RESULTING IN MORE BACK BUILDING STORMS WITH LONGER PERIODS
OF HIGHER RAINFALL RATES, IN SOME INSTANCES OVER 2 INCHES PER
HOUR. MIXED LAYER CAPE NEAR 3000 J/KG PER RECENT SPC MESOANALYSIS
AND PWS NEAR 2 INCHES ARE PRESENT NEAR AND JUST SOUTH OF THE
ONGOING CONVECTION.
ALTHOUGH SEVERE WEATHER HAS BEEN THE PRIMARY THREAT THUS FAR WEST
OF THE ROCKFORD AREA, THE POTENTIAL FOR FLASH FLOODING WILL
INCREASE OVER THE NEW FEW HOURS AS ADDITIONAL STORMS DEVELOP AHEAD
OF THE MAIN LINE. THERE IS GOOD OVERALL AGREEMENT IN THE LATEST
CAM GUIDANCE SUITE, INCLUDING THE CURRENT WOFS, FOR A SWATH OF
ADDITIONAL 1-3 INCH TOTALS THROUGH 19Z, WITH MUCH OF THIS FALLING
WITHIN A 60-90 MINUTE TIME PERIOD FOR ANY GIVEN LOCATION. RAINFALL
RATES SHOULD TAPER OFF AFTER THE MAIN SQUALL LINE MOVES THROUGH.
HAMRICK
..PLEASE SEE WWW.WPC.NCEP.NOAA.GOV FOR GRAPHIC PRODUCT
ATTN...WFO...CLE...DTX...DVN...GRR...ILX...IND...IWX...LOT...
MKX...
ATTN...RFC...MSR...TIR...NWC...
LAT...LON 43318927 43248664 43038547 42558324 41458328
40818463 40348680 40228898 40738998 41409004
42048937 42958963
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