Destructive storms and violent lightning shake Chicago with new round forecast

Significant, severe thunderstorms, some of hurricane force, are expected across much of the Midwest and Great Lakes region on Monday evening, following a series of severe storms overnight from Sunday to Sunday.

Chicago — which saw wind gusts of about 60 mph Sunday night — is right in the center of Monday’s greatest storm threat. Thunderstorms capable of producing wind gusts over 75 mph and a few tornadoes are expected to move east toward Indianapolis late Monday night before easing off.

The National Weather Service’s Storm Prediction Center has rated the area from Des Moines east to Valparaiso, Indiana, at risk level 3 of 5 for severe storms. It includes Chicago, Aurora, Rockford, Naperville and Joliet in Illinois. Milwaukee and Indianapolis are at risk level 2 of 5.

The storms in Chicago on Sunday night produced gusts of 59 mph at Midway Airport, 67 mph over Lake Michigan just a few miles offshore, and 70 mph at DuPage Airport. Numerous large branches and some trees fell from 48th and State Streets to 46th Street and MLK Drive in downtown. There was even a brief tornado in the southwest suburbs, confirmed by radar. A tornado warning was in effect for downtown Chicago until 11 p.m.

Even after the storms passed, the remaining positive charge in the upper parts of the storm contributed to multiple lightning bolts striking upward from the skyscrapers at the same time; at 12:21 a.m., three lightning bolts struck simultaneously from the Hancock, Trump, and Sears towers.

The timing of the storms on Monday

The storms forecast for Monday evening could be even more severe than those on Sunday.

Thunderstorms should develop quickly in central or eastern Iowa around 6 p.m., then move quickly eastward and reach northwest Illinois by sunset. The first scattered thunderstorms may contain hailstones up to the size of golf balls before consolidating into a squall line with damaging winds. They are then expected to sweep through Chicago around 9 p.m. (give or take an hour) and continue to move southeast. Thunderstorms could develop in Indianapolis around midnight. Thunderstorms will die down east of Indianapolis.

How the storms can come together

On Monday, a low pressure system will pass north of Lake Michigan. It will be preceded by an exceptionally warm and humid climate with a summery steamy air mass. A cold front drawn eastward by the low pressure system will act as a trigger, pushing up this moisture and instability, or storm fuel, which could lead to severe storms.

With a strong jet stream overhead, storms that get high enough are likely to the strong high-altitude winds. Some may be able to transport these strong high-altitude winds to the surface in the form of destructive gusts.

There’s even a small chance that the squall line could develop into a derecho. These powerful storms produce widespread gusts of 60 mph and some gusts over 80 mph that travel at least 400 miles.

In addition, the atmosphere will have a low-level vortex or rotation. This could favor short-lived tornadoes on the leading edge of the squall line. While tornadoes would be short-lived, they would develop quickly and move erratically. Regardless of whether a tornado warning is in place, it is a good idea to seek shelter during approaching storms.

The National Weather Service will issue warnings in the afternoon, which implies the likelihood of severe weather later. As storms approach, warnings are issued Warnings are issued for areas at risk of damage. If a storm is classified as “destructive” and produces gusts of 80 miles per hour or more, wireless emergency alerts are automatically activated on smartphones.