Update 9:15AM CDT…
As of 9AM CDT strongest thunderstorms were moving southeast through southwestern portions of the Chicago area, and due to locally heavy rainfall of 1 to 2-inches (indicated by weather radar) a Flood Advisory for minor flooding has been issued for portions of Lee, DeKalb, Kendall, Will, LaSalle and Grundy Counties until 11AM CDT.
While rain has diminished significantly in other areas, strong southerly winds have picked up gusting to 45-50 mph at times across portions of Lake, Kane, DuPage and Cook Counties. These winds should slowly diminish somewhat later this morning.
This wide-spread cloudiness and shower/thunderstorm activity has disrupted the lower portions of the atmosphere over the Chicago area and may well result in significantly diminished chances of severe storm development this afternoon. We will continue to monitor conditions as afternoon heating picks up.
A Mesoscale Convective System of showers/thunderstorms is moving south out of Wisconsin into northern Illinois early Tuesday morning.
A few of the strongest storms could produce brief heavy downpours, small hail and winds gusting to around 40 mph.
The system of showers/thunderstorms should be slowly weakening as it moves southeast at about 30 mph.
After this system dies out, a band of strong thunderstorms could redevelop ahead of an approaching cold front, again out of Wisconsin this afternoon – some of these storms could become severe with damaging winds and large hail. Where this line develops will depend upon how far south the mesoscale system spreads and stabilizes conditions this morning over northern Illinois. A good portion of the Chicago area is under a Slight risk of Severe storms today (yellow-shaded area on the map below).