Chicago weather live: Tornado warning , thunderstorm warnings, ground stop at O'Hare as line barrels into area

The Chicago area is under an enhanced risk for severe weather Tuesday, with severe storms and a damaging derecho both in the forecast.  

There is a ground stop at Chicago O'Hare International Airport due to thunderstorms, as well as a ground delay for flights averaging 144 minutes due to the storms. 

A Tornado Warning for Cook, DuPage, Kendall, Kane and Will counties until 11 a.m. 

A Severe Thunderstorm Warning is in effect for Jasper, Porter and Lake counties in Indiana until 10:30 a.m., for Kane and McHenry counties until 10:45 a.m. and for Grundy, La Salle, Kendall and Livingston counties in Illinois and La Porte County in Indiana until 11 a.m.

A Severe Thunderstorm Watch is in effect for LaSalle, Kane, Kankakee, Grundy, Will, Cook, DeKalb, DuPage, McHenry, Kendall,  and Lake counties in Illinois and Newton, Jasper, Porter and Lake counties in Indiana until 2 p.m.  and for La Porte County until 4 p.m. CDT. 

A Flood Advisory has been issued for Boone, DeKalb, LaSalle, Lee, Ogle and Winnebago counties until 1:30 p.m. and Grundy, Kane and Kendall counties until 2 p.m.

The main window for severe weather in the area is expected to be about 9:30 a.m. through 1:30 p.m. The greatest risks are for flooding and wind damage, as a derecho in Iowa is barreling due east toward the area and is expected to cut a path of destruction through the Chicago area and Northwest Indiana. 

Wind gusts of 80 to 95 mph are possible during these storms, with more isolated gusts over 95 mph. Hurricane force wind gusts over 70 miles per hour have already been detected by doppler radar near Sycamore in DeKalb County as of 10 a.m.

The storms are expected to reach the city by about 11 a.m.

There are outflow boundaries along the central and southern lines of the storm which could produce tornado warnings as the line of squall storms reaches it. 

The storms are forecast to move east-southeast through the Chicago metro and Northwest Indiana.

Heavy rainfall will also be a concern, especially across Chicago, which already received up to 5 inches of rain by Sunday night. Localized flooding could develop where storms repeatedly track over the same areas.

Storm activity should decrease later Tuesday afternoon into tonight, but the overall weather pattern remains active, with additional chances for thunderstorms continuing through the end of the week and into the weekend.

What is a derecho?

A derecho is defined by the National Weather Service as a complex of thunderstorms that produces a relatively unbroken line of wind damage measuring at least 240 miles in length with wind gusts at least 58 miles per hour along its path. 

In 2020, a massive derecho with winds around 100 mph cut a path of devastation across the Midwest, including the Chicago area and Northwest and Central Indiana, causing an estimated $11 billion in damage. In 2009 a Super Derecho was recorded as one of the strongest on record, traveling more than 1,000 miles in 24 hours and causing $500 million in damage as well as a handful of deaths.

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