A center of low pressure will be moving east through Minnesota today while a warm front extends east across northern Wisconsin and the associated cold front sweeps east into Iowa. Illinois rests in the “warm sector” of this system with southerly winds pulling warm moist unstable air out of the central plains into the Midwest and western Great Lakes.
A band of showers and a few thunderstorms will work northeast through central into northern Illinois this morning with stronger – potentially severe storms expected to develop over northeast Illinois, southeast Wisconsin, northwest Indiana into southern Lower Michigan later this afternoon into tonight.
As this weather system advances east, the cold front should sweep through the Chicago area later Tuesday. The threat of strong potentially severe storms here could carry-over from Monday night into Tuesday morning.
In the severe weather outlook map below, much of illinois, Indiana, Wisconsin and Lower Michigan are in the slight risk areas for later today and tonight. The slight risk is approximently a 15 percent chance of damaging hail and winds in excess of 58 mph as well as a 5 percent chance of tornadoes within 25 miles of a given point.