Skies have been pretty dry and temperatures comfortable following Monday’s derecho event which produced a total of 15 tornadoes across northern Illinois. Four of those tornadoes occurred in the immediate viewing areas of Winnebago, McHenry, Boone and DeKalb counties. High pressure was quick to build for the remainder of the week leaving skies dry through Friday night.
A quickly advancing cold front over the Plains and Midwest will pass through Wisconsin and Illinois Saturday. Severe thunderstorms have developed along the front Friday evening with numerous tornado warnings ongoing in Minnesota. The risk for strong to severe storms will remain across the Midwest and Plains Friday evening, with cloud cover increasing locally overnight. Temperatures will dip into the mid 60s for the start of Saturday.
A few light showers may be possible before sunrise Saturday but with drier air overhead a lot of the rain will fizzle out before reaching the Stateline. An earlier arrival of the cold front Saturday means most of the storm activity for the afternoon will develop along and east of I-39, and closer towards Chicago and Indiana during the late afternoon and evening. While a few isolated thunderstorms will be possible for the immediate area early afternoon, there remains a higher chance for strong/severe storms to the east. This is where the Storm Prediction Center has placed the ‘marginal risk’ for severe storms during the afternoon. Locally, a few gustier storms may be possible but will remain rather isolated. Drier air along with high pressure will help clear skies Saturday night and heading into Sunday.