Massive, destructive storm front to wreak havoc in the Midwest

(CNN) — The Windy City better watch out, as things could get really windy and really dangerous — really quick.

Chicago is one of several Midwest cities and towns that is facing a “high risk” — the most perilous category — of severe weather from Wednesday afternoon into the night, according to the National Weather Service’s Storm Prediction Center.

This endangered area includes parts of Indiana, Ohio as well as much of Illinois.

The portion of the United States under a moderate risk for severe weather extends farther, and includes the cities of Cedar Rapids, Iowa; Indianapolis, Indiana; and Columbus, Ohio.

The bad weather — in the form of severe thunderstorms, large hail and damaging winds — is “expected to develop rapidly,” the Storm Prediction Center’s advisory warns.

The threat of tornadoes was particularly high in southwest Wisconsin and northwest Illinois.

Parts of north central Iowa were under a tornado warning due to reports of a “confirmed tornado” 8 miles east of Belmond, according to the weather service. There was no immediate word of damage or casualties.

Such warnings were issued for parts of Illinois and Wisconsin, thanks to severe thunderstorms capable of producing a twister.

In the Chicago area, that likely will mean up to 3 inches of pounding rain and 80 to 100 mph winds, said National Weather Service meteorologist Amy Seeley.

“We have the main threat anywhere between 6 and 11 p.m.,” said Seeley.

Some in the region were taking precautions in advance, such as the decision to cancel Wednesday night’s game between the Chicago White Sox and Toronto Blue Jays at Chicago’s U.S. Cellular Field.

Russ Schneider, director of the Storm Prediction Center, explained that the type of severe weather that’s expected to develop in the Upper Midwest is a derecho.

Derived by the Spanish word for “straight ahead,” derechos are a weather phenomenon that traditionally happens only a few times a year. It is defined as a line of storms that produces a swath of damage more than 240 miles long with gusts of at least 58 mph.

A derecho forms thanks in large part to warm, humid air, instability in the atmosphere and jetstream winds, which can organize the storms into isolated storms called super cells.

Those super cells rotate among themselves, then cluster into powerful wind systems that can become derechos, Schneider said.

A line of such storms travels quickly — often at around 50 to 60 mph, which is much faster than most other types of storms.

“(So) what looks like a very dark cloud on the horizon very rapidly becomes an imminent threat,” explained Schneider. “(People should) make sure they know where they go to seek shelter, and what actions they need to take as warnings are issued.”

In its weather outlook, the storm prediction center said: “Those in the threatened area are urged to review severe weather safety rules and to listen to radio, television and NOAA weather radio for possible watches, warnings and statements later today.”

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