A big winter storm is developing for midweek.

A Winter Weather Advisory is in effect from 6 a.m. Wednesday through 6 a.m. Thursday for Boone, DeKalb, Kane, Lake, McHenry, Ogle and Winnebago counties in Illinois.

Freezing rain, sleet and ice are possible. Hazardous road conditions could impact morning and evening commutes.

Latest warnings and watches from the National Weather Service.

Major rains expected in Chicago

For Chicago, the main threat is heavy rainfall.

Perhaps the biggest rain in more than two months will arrive starting mid-morning Wednesday. Scattered rains could be parts of the area as early as 6 a.m to 8 a.m.

Rainfall could reach 1.4 to 1.6″–which if that verifies, would be the heaviest city rain since Dec—and some embedded t-storms can’t be ruled out

Ice could be an issue

Ice could become a real issue north and west of the city. A quarter to half inch of ice may accumulate in near freezing temps Wednesday afternoon and night basically north of the I-88 corridor and away from Lake Michigan.

Looks like sections of Lake, McHenry, Boone and Winnebago counties are at risk for an ice buildup. This would include Belvidere, McHenry, Woodstock, Poplar Grove, the Rockford area—essentially areas along and either side of the Wisconsin line.

At least some icing could extend south to the northern Fox Valley area and perhaps northern DeKalb County.

Temperatures a critical factor

Temps just a few degrees warmer than those predicted (hovering around freezing) could cut down on the ice threat. But icing may well be an issue.

Strong winds expected

East winds will build to 30 mph in gusts across the entire Chicago area Wednesday into Wednesday night. They will then ease a bit Thursday morning only to roar back and approach 50 mph in gusts Thursday afternoon and evening. Some sort of Wind Advisory may become necessary Thursday afternoon and evening.

Latest warnings and watches from the National Weather Service.

Beyond Chicago

Farther north—a snowstorm with near blizzard or blizzard conditions likely from central and northern Wisconsin west across the Twin Cities and Minnesota into the Dakotas. 

The Wed/Thu storm which is to bring rain, wind and ice to sections of the Chicago area–threatens what’s being billed there as a potentially historic snowstorm—one with near blizzard conditions to the upper Midwest including the Twin Cities where snowfalls of 16-24″ seem likely. If true, this could rank among the heavier snowstorms to hit Minneapolis—and that’s a city which has seen some real doozies!