The latest on the winter storm is that the Winter Storm Warnings have been extended to include much of the Chicago metro areas. Counties included are Cook, DuPage, Lake, Lee, DeKalb, Kane, La Salle, Grundy, Will, Kankakee, Iroquois, and Ford counties in Illinois and Lake, Porter, La Porte, Benton, Jasper, and Newton counties in Indiana. The Winter Storm Warning is in effect to 6pm CST Sunday.
The far northwestern counties (Boone, Winnebago, and Ogle) have been excluded from the warnings. This includes the city of Rockford. However, a coating of light snow cannot be ruled out in these areas this evening.
Behind the snow will come an incredibly cold airmass not witnessed for quite some time. A piece of what's known as a polar vortex (a large-scale upper level cyclonic feature that's located near the poles and is associated with very cold air at the surface) will bring potentially record breaking temperatures into the northern Plains and Midwest including the Chicago area Sunday night through Tuesday. A Wind Chill Warning is also in effect for the area.
Details - NWS text of the Winter Storm and Wind Chill Warnings for the Chicago area:
FOR THE WINTER STORM WARNING...
* TIMING...SNOW IS EXPECTED TO CONTINUE...HEAVY AT TIMES...TONIGHT
* MAIN IMPACT...PERIODS OF HEAVY SNOW TONIGHT INTO SUNDAY WILL
RESULT IN 5 TO 10 INCHES OF NEW SNOW ACCUMULATION...LEADING TO
HAZARDOUS TRAVEL CONDITIONS.
* OTHER IMPACTS...BRISK NORTHWEST WINDS OF 20 TO 30 MPH WILL
RESULT IN CONSIDERABLE BLOWING AND DRIFTING SNOW WITH REDUCED
VISIBILITY...PARTICULARLY SUNDAY AFTERNOON AND NIGHT.
FOR THE WIND CHILL WARNING...
* TIMING...A PROLONGED PERIOD OF DANGEROUSLY COLD WIND CHILLS
ARE EXPECTED SUNDAY NIGHT THROUGH TUESDAY MORNING. WHILE
DANGEROUS WIND CHILLS ARE LIKELY THROUGH THE PERIOD...THE MOST
EXTREME WIND CHILLS ARE LIKELY TO BE LATE SUNDAY NIGHT THROUGH
* WIND CHILLS...A PROLONGED PERIOD OF WIND CHILLS COLDER THAN 30
BELOW IS EXPECTED...WITH WIND CHILLS OF 40 TO 50 BELOW
EXPECTED LATE SUNDAY NIGHT INTO MONDAY AFTERNOON.
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