NORTHEAST ILLINOIS AND NORTHWEST INDIANA.
.DAY ONE...TODAY AND TONIGHT.
WEATHER HAZARDS EXPECTED:
HEAT INDEX VALUES FROM 103 TO 109
THUNDERSTORMS...A FEW MAY PRODUCE
DAMAGING WIND GUSTS IN EXCESS OF 60 MPH
LARGE HAIL
HEAVY RAINFALL
ISOLATED TORNADOES
AREAS AFFECTED AND TIMING:
HEAT INDEX VALUES WILL RANGE FROM 103 TO 109 DEGREES FROM LATE
THIS MORNING THROUGH THIS AFTERNOON ACROSS ALL OF NORTH CENTRAL
AND NORTHEAST ILLINOIS AND NORTHWEST INDIANA.
THUNDERSTORM CHANCES WILL INCREASE FROM NORTH TO SOUTH ACROSS
THE ENTIRE OUTLOOK AREA FROM LATE THIS AFTERNOON THROUGH THIS
EVENING.
DISCUSSION:
A COLD FRONT WILL PUSH SOUTHEASTWARD FROM MINNESOTA AND WISCONSIN
TODAY. A VERY WARM AIRMASS WILL DRIFT INTO NORTHERN ILLINOIS AND
NORTHWEST INDIANA TODAY ALLOWING TEMPERATURES TO WARM INTO THE MID
AND UPPER 90S. THIS WILL COMBINE WITH DEWPOINTS IN THE MID 70S TO
CREATE HEAT INDEX VALUES FROM 103 TO 109 DEGREES. THE FRONT WILL
REACH THE NORTHERN ILLINOIS BORDER BY EVENING BRINGING INCREASING
CHANCES FOR THUNDERSTORMS. THUNDERSTORM ACTIVITY WILL PUSH
SOUTHWARD INTO NORTHERN ILLINOIS AND NORTHWEST INDIANA DURING THE
EARLY EVENING HOURS. CHANCES FOR AND COVERAGE OF STORMS WILL BE
HIGHEST ACROSS NORTHEAST ILLINOIS AND NORTHWEST INDIANA WITH
SLIGHTLY LOWER CHANCES ACROSS NORTH CENTRAL ILLINOIS. THE MAIN THREAT
WILL BE DAMAGING STRAIGHT LINE WINDS AND HEAVY DOWNPOURS. LARGE
HAIL WILL ALSO BE POSSIBLE AND THERE WILL BE SUFFICIENT LOW LEVEL
WIND SHEAR TO SUPPORT AN ISOLATED TORNADO THREAT. THE STORMS WILL
BE EFFICIENT RAINFALL PRODUCERS SO A QUICK INCH OR SO OF RAIN WILL
CERTAINLY BE POSSIBLE BUT STORMS ARE EXPECTED TO BE MOVING ALONG
STEADILY. THIS WILL KEEP THE THREAT OF FLASH FLOODING LOW. SOME
STORMS MAY LINGER SOUTH OF INTERSTATE 80 AFTER MIDNIGHT.
.DAYS TWO THROUGH SEVEN...WEDNESDAY THROUGH MONDAY.
THERE IS ANOTHER CHANCE OF THUNDERSTORMS THURSDAY NIGHT THROUGH
FRIDAY...THEN AGAIN SATURDAY NIGHT THROUGH MONDAY.
THERE IS AN INCREASED RISK OF RIP CURRENTS ALONG THE INDIANA
SHORE OF LAKE MICHIGAN WEDNESDAY.
.SPOTTER INFORMATION STATEMENT...
SPOTTERS MAY BE NEEDED FROM LATE THIS AFTERNOON THROUGH THIS
EVENING.
&&
COMPLETE FORECAST INFORMATION IS AVAILABLE ON THE NWS CHICAGO
WEBPAGE: WEATHER.GOV/CHICAGO
