Risk of strong to severe thunderstorms here increases Wednesday, then continues Thursday into Friday
The National Storm Prediction Center has included the Chicago area (northeast Illinois into northwest Indiana) in a Slight to Marginal Risk of severe thunderstorms beginning later today and tonight through Thursday into Friday (see highlighted map for Wednesday/Wednesday night and maps below for Thursday and Friday. The yellow-shaded Slight Risk area depicts a 15% chance of severe storms within 25 miles of a given location, while the dark-green-shaded Marginal Risk area depicts a 5% chance of severe storms within 25 miles of a given location. The storm potential will include damaging winds, large hail and flood-producing downpours.
With strong southwest winds bringing/maintaining increasingly warm moist unstable air overhead and a slow-moving low pressure and associated cold front to our west, timing of the severe storms will most likely coincide with the peak-heating portion of the afternoon into the evening hours each day.
Wednesday the shower/thunderstorm cluster over Iowa (note the highest tan-shaded Enhanced Severe Storm Risk is centered over Iowa) is expected to weaken as it moves east into Illinois, the remnant storms possibly weakened considerably by the time they reach our area midday. Strong to severe storms are forecast to redevelop to our west and spread into our area this evening/overnight.
Thursday and Friday timing and placement of storms is difficult, and they could occur anywhere across our area, but the best chances appears to be later afternoon into the evening hours along and south of Interstate-80. The passage of the cold front should bring an end to the severe storm threat later Friday.
Thursday severe weather outlook map…
Friday Severe weather outlook map…