A strong thunderstorm that tracked east along Interstate-80 had a peak wind gust estimated between 65 and 70 miles per hour in the Downers Grove area (DuPage County) around 10:20AM this morning. Just prior to that, there were several reports of pea to marble-size hail in the Aurora area. Farther east the same thunderstorm complex dropped half-inch diameter hail in the Hobart, Indiana area around 11:30AM CDT..
Update 8:50AM CDT..
The Flash Flood Warning for northwest McHenry, Winnebago and Boone counties expired at 8:30AM and was replaced by a Flood Advisory until 11:30AM CDT for northern Winnebago and northern Boone Counties. Additional rains this morning of three-quarters inch to an inch and a half on top of overnight rains have increased the potential for temporary rises on local streams and minor flooding this morning.
Also the National Storm Prediction Center has updated the slight risk of severe storm area (check out yellow-shaded expanded slight risk area on map below).
Update 7:45AM CDT…
A complex of showers and thunderstorms tracking south of a the previous southern Wisconsin band – will move quickly east across northern Illinois passing over and north of the Chicago area mid-to-late morning.
A complex of strong thunderstorms moving east across southern Wisconsin and southern Lake Michigan has dipped south into the Illinois counties adjacent to the Illinois-Wisconsin state line early this morning. Heavy rains on top of already saturated soils has prompted the issuance of a Flash Flood Warning in effect until 8:30AM CDT this morning for northwest McHenry, Winnebago, and Boone Counties.
With more strong – possibly severe thunderstorms expected to develop and move out of Iowa across southern Wisconsin and northern Illinois this afternoon-evening, a Flash Flood Watch is in effect until Wednesday morning for Boone, DeKalb, Lee, Ogle and Winnebago Counties. Depending on how conditions develop, this watch may be extended to cover most of northeast Illinois into northwest Indiana today.
The National Storm Prediction Center again has northern Illinois – including Chicago as well as southeastern Wisconsin and northwest Indiana (yellow shaded area on map below) included in the slight risk area for severe thunderstorms today and tonight, with the strongest potential looking to be this afternoon into this evening. Greatest threat here in the Chicago area will be strong winds, although the possibility of large hail and even a tornado or two may also exist.
Slight risk of severe thunderstorms today (Tuesday) and tonight