CHICAGO — The National Storm Prediction Center has northeast Illinois into the northwest corner of Indiana, generally along and north of the Interstate-80 corridor in a Slight Risk for Severe Thunderstorms late Thursday afternoon into the overnight hours (yellow-shaded area on the highlighted map depicting a 15% chance of severe storms within 25 miles of a given location).
The remainder of the Chicago area to the south is in a Marginal Risk (dark-green-shaded area depicting a 5% chance of severe storms within 25 miles of a given location). The primary threat will be for damaging winds and large hail.
A warm front will be moving north through our area today with warm humid air supporting high afternoon temperatures in the lower 90s and dew points in the upper 60s to lower 70s with ongoing showers and thunderstorms north of the front across Wisconsin.
A cold front will approach our area from the west, crossing the Mississippi River later this afternoon with strong to severe thunderstorms developing along and ahead of the frontal boundary. The thunderstorms will move into westernmost sections of our area along and west of Interstate-39 late this afternoon and then continue to march east as the cold front tracks from west to east through northern Illinois eventually into northwest Indiana overnight into the early morning hours Friday. Cooler drier Canadian-source high pressure will follow the cold front into our area Friday, as the showers/thunderstorms move off to the east.