Meteorologists warn that the continuous line of storms may result in an unusual weather event called a derecho, a massive storm packing strong straight-line winds spanning up to 240 miles.
Thursday’s storms will also likely spawn tornadoes and result in power outages that will be followed by oppressive heat, says Bill Bunting, operations chief at the National Weather Service‘s Storm Prediction Center in Oklahoma.
Detroit, Baltimore, Washington, Milwaukee, Pittsburgh and Louisville, Kentucky have a risk level for severe storms that is 15 times greater than normal.
“It’s a pretty high threat,” Bunting said, who added that the storms will produce hail and lots of lightning. “We don’t want to scare people, but we want them to be aware.”
Thursday “might be the worst severe weather outbreak for this part of the country for the year,” said Jeff Masters, meteorology director at Weather Underground.
Derechoes, packing winds of at least 58 mph, take place about once a year in the Midwest. Rarer than tornadoes but with weaker winds, derechoes produce damage over a much wider area.
More in the video below.