645
AWUS01 KWNH 040420
FFGMPD
INZ000-ILZ000-040715-
MESOSCALE PRECIPITATION DISCUSSION 0079
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
1219 AM EDT SAT APR 04 2026
AREAS AFFECTED...NORTHEASTERN ILLINOIS, NORTHWESTERN INDIANA
CONCERNING...HEAVY RAINFALL...FLASH FLOODING POSSIBLE
VALID 040415Z - 040715Z
SUMMARY...TRAINING CONVECTION COULD PERSIST FOR ANOTHER COUPLE
HOURS INTO SOUTHERN SUBURBS OF CHICAGO METRO.
DISCUSSION...A PERSISTENT, SW-NE ORIENTED BAND OF CONVECTION HAS
TRAINED ALONG AN AXIS VERY NEAR I-55 BETWEEN JOLIET AND PONTIAC
OVER THE PAST COUPLE HOURS. THE CONVECTION IS BECOMING
PROGRESSIVELY MORE ELEVATED WITH TIME, BUT IS PERSISTENT WITHIN A
WARM-ADVECTION REGIME LOCATED JUST ABOVE A STABLE BOUNDARY LAYER,
WITH ~1000 J/KG MUCAPE (PER SPC MESOANALYSES) SUPPORTING STRONG
UPDRAFTS. THE ORIENTATION OF THE CONVECTION WAS SUPPORTING
PROLONGED RAINFALL, LEADING TO RATES IN THE 1-2 INCH/HR RANGE
(1-2X HIGHER THAN ESTIMATED FFG IN THE REGION). DOWNSTREAM
INSTABILITY PROFILES ARE SUPPORTIVE OF THIS BAND OF CONVECTION
REACHING SOUTHERN SIDES OF CHICAGO METRO AND FAR NORTHWESTERN
INDIANA OVER THE NEXT COUPLE HOURS, RESULTING IN AT LEAST ISOLATED
FLASH FLOOD POTENTIAL. OUTSIDE OF THIS BAND, DEEPENING SHOWERS
WERE NOTED ACROSS A BROADER PORTION OF NORTHERN AND CENTRAL
ILLINOIS THAT MAY REPEAT OVER SOME OF THE SAME AREAS IN LINE FOR
HEAVY RAIN FROM THE AFOREMENTIONED BAND, BUT DEGREE OF
TRAINING/HIGH-RAIN RATES IS UNCERTAIN.
COOK
..PLEASE SEE WWW.WPC.NCEP.NOAA.GOV FOR GRAPHIC PRODUCT
ATTN...WFO...IWX...LOT...
ATTN...RFC...MSR...NWC...
LAT...LON 41888715 41528688 40948779 40988829 41278872
41738828
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