Deepening low pressure will track rapidly NE across the Chicago area Thursday. 

Combined with a strong jet stream flow aloft, the increasingly unstable atmosphere will produce locally heavy rains during the morning rush hour and strong winds shifting from the east to the southwest and finally the northwest 20-40 mph.  As colder air follows behind the departing low pressure, temps will fall and the rain could be mixed with or change over to wet snow especially in northern portions of the area. 

Heavy Snows, Heavy Rains, Damaging Winds

Heavy snow 4 to 8+ inches are expected from NE Iowa through Wisconsin, across lower Michigan into southern Ontario, Canada.
Heavy rains 1+ inch from the Gulf Of Mexico north to Chicago and Lower Michigan. Severe storms with damaging winds possible south and east of Chicago across most of Indiana and Ohio.