UPDATE 5:30PM: A cold front sweeping across southern Wisconsin into northern Illinois remains fairly inactive on this hot, late Friday afternoon. Very little if any shower or thunderstorm activity has been noted through 5:30PM.
The latest computer model guidance continues to stir up a few scattered thunderstorms across northern Illinois and northwest Indiana between 6PM and 10PM. Coverage on any storms that do develop may be limited to around 20% to 40% of the area, due to weak surface wind convergence. At this point, it appears many Chicago area towns and neighborhoods will miss out on the rain due to the limited coverage.
It is interesting to note that the surface convergence is considerably more favorable over Lake Michigan, so the best chance of rain tonight is expected to be just east of Chicago, over the lake and into southwest Michigan.
3:15PM A strong cold front will sweep across the Chicago area this evening ushering in drier and cooler air for the weekend. As the front passes through the region, scattered strong thunderstorms are expected to develop between 4PM and 7PM. The storms should then quickly exit the area between 9PM and Midnight.
Due to weak surface convergence (a key component in initiating thunderstorm development in this scenario) , the storms that do develop are expected to be of the “scattered” variety, meaning some Chicago area towns and neighborhoods may miss out on the rain altogether. Those that do see the storms can expect heavy downpours, frequent lightning and gusty winds. A few of the storms may turn severe, with wind gusts in excess of 58mph.
Check back with us throughout the afternoon and evening for updates as we monitor the situation from the WGN Weather Center.
BELOW: The latest in house RPM model depicts the timing and “hit or miss” nature expected from this evening’s storms.