Bands of showers and thunderstorms will develop along and ahead of a cold front as it moves slowly south across northeast Illinois into northwest Indiana this Wednesday afternoon into the overnight hours. The very warm humid unstable conditions ahead of the front will be further destabilized as the cold front approaches and passes through a given location. In addition to vivid lightning, stronger t-storms could be accompanied by small hail and wind gusts as high as 45 to mph as they track off to the east. The Chicago area is under a Marginal Risk for severe storms this afternoon and tonight (green-shaded area on headlined severe weather outlook map.
Showers and t-storms will gradually end from the north and west later tonight and early7 Thursday morning. The maps below show about a 40% to 50% chance of t-storms within 12 miles of a given location (blue-shaded area on the maps) over much of our area until about 11PM, then probability drops to 10 to 20% (brown-shaded area).