NORTHEAST ILLINOIS AND NORTHWEST INDIANA.
.DAY ONE...TONIGHT.
WEATHER HAZARDS EXPECTED:
THUNDERSTORMS...SOME MAY PRODUCE:
WIND GUSTS UP TO 60 MPH.
HEAVY RAINFALL.
ISOLATED TORNADOES.
FREQUENT LIGHTNING.
AREAS AFFECTED AND TIMING:
ISOLATED THUNDERSTORMS MAY DEVELOP ALONG A LINE FROM ROCKFORD
EASTWARD ACROSS THE NORTHERN CHICAGO METRO LATE THIS AFTERNOON.
MORE WIDESPREAD THUNDERSTORMS ARE EXPECTED TO DEVELOP ACROSS
EASTERN IOWA OR NORTHWEST ILLINOIS LATE THIS AFTERNOON AND EARLY
THIS EVENING THEN MOVE EASTWARD INTO NORTH CENTRAL AND NORTHEAST
ILLINOIS...PRIMARILY ALONG AND NORTH OF INTERSTATE 88 AND
INTERSTATE 290. AREAS SOUTH OF THESE HIGHWAYS HAVE A CHANCE FOR
THUNDERSTORMS AS WELL. THUNDERSTORMS WILL LIKELY CONTINUE
THROUGH THE NIGHT ALONG AND NORTH OF INTERSTATE 80.
DISCUSSION:
A WARM FRONTAL BOUNDARY LIFTING NORTHWARD ACROSS NORTHERN
ILLINOIS WILL BE THE FOCUS FOR THUNDERSTORM DEVELOPMENT LATE
THIS AFTERNOON THROUGH TONIGHT. IT APPEARS THAT THUNDERSTORMS
WILL BEGIN TO DEVELOP ACROSS EASTERN IOWA NORTHWEST ILLINOIS
LATE THIS AFTERNOON WITH SOME ISOLATED DEVELOPMENT POSSIBLE
ACROSS NORTH CENTRAL AND NORTHEAST ILLINOIS. THUNDERSTORM
ACTIVITY IS THEN EXPECTED TO MOVE EASTWARD AND BECOME MORE
WIDESPREAD THROUGH THE EVENING AND CONTINUE OVERNIGHT. WITH A
VERY MOIST AIR MASS IN PLACE EXTREMELY HEAVY DOWNPOURS ARE LIKELY
UNDER THE STRONGEST STORMS WITH RAINFALL RATES OF 1 TO 3 INCHES
PER HOUR POSSIBLE. PLACEMENT OF THE FRONT WILL BE KEY IN
IDENTIFYING THE AREA WHERE THE HEAVIEST RAIN WILL FALL. AT THIS
TIME...THERE IS POTENTIAL FOR HEAVY RAIN AND FLASH FLOODING
ALONG AND NORTH OF INTERSTATE 80 INTO FRIDAY MORNING. THE
GREATEST THREAT FOR FLASH FLOODING WILL BE ALONG AND NORTH OF
INTERSTATE 88 AND INTERSTATE 290. IN ADDITION...STREAMS AT OR
NEAR BANKFULL MAY BECOME FURTHER SWOLLEN AS A RESULT OF ANY
HEAVY RAINFALL.
HIGH HEAT AND HUMIDITY WILL BE A CONCERN ACROSS AREAS FROM
PONTIAC TO KANKAKEE TO RENSSELAER WITH HEAT INDEX VALUES BETWEEN
100 AND 110 DEGREES UNTIL EARLY EVENING.
.DAYS TWO THROUGH SEVEN...THURSDAY THROUGH TUESDAY.
THERE IS A CHANCE FOR THUNDERSTORMS THURSDAY THROUGH FRIDAY.
THUNDERSTORMS MAY PRODUCE VERY HEAVY RAINFALL... ESPECIALLY FOR
LOCATIONS NORTH OF THE INTERSTATE 80 CORRIDOR.
HEAT AND HUMIDITY RETURNS TO NORTHERN ILLINOIS AND NORTHWEST
INDIANA THURSDAY...MAINLY SOUTH OF INTERSTATE 80 WHERE HEAT
INDICES WILL RANGE FROM 100 TO 110 DEGREES.
.SPOTTER INFORMATION STATEMENT...
SPOTTERS MAY BE NEEDED THIS EVENING AND TONIGHT.
&&
COMPLETE FORECAST INFORMATION IS AVAILABLE ON THE NWS CHICAGO
WEBPAGE: WEATHER.GOV/CHICAGO
