Violent storms cut through a wide swath of the South and Midwest, spawning tornadoes and killing at least one person, knocking down power lines and trees and ripping roofs off homes.

Dozens of tornado and severe thunderstorm warnings were issued Wednesday in parts of Arkansas, Illinois, Indiana, Missouri and Mississippi as storms hit those and other states in the evening. Forecasters attributed the violent weather to daytime heating combining with an unstable atmosphere, strong wind shear and abundant moisture streaming into the nation’s midsection from the Gulf.

At least one person was killed in southeast Missouri, KFVS-TV reported, while part of a warehouse collapsed in a suburb of Indianapolis, temporarily trapping at least one person inside. In northeast Arkansas a rare tornado emergency was issued as debris flew thousands of feet in the air.

The coming days were also forecast to bring the risk of potentially deadly flash flooding to the South and Midwest as severe thunderstorms blowing eastward become supercharged. The potent storm system will bring “significant, life-threatening flash flooding” each day through Saturday, the National Weather Service said.

With more than a foot (30 centimeters) of rain possible over the next four days, the prolonged deluge “is an event that happens once in a generation to once in a lifetime,” the weather service said. “Historic rainfall totals and impacts are possible.”

More than 90 million people were at some risk of severe weather in a huge part of the nation stretching from Texas to Minnesota and Maine, according to the Oklahoma-based Storm Prediction Center.

Tornadoes touch down, and more could be coming

A tornado emergency — the weather service’s highest alert — was briefly declared around Blytheville, Arkansas, on Wednesday evening, with debris lofted at least 25,000 feet (7.6 kilometers), according to Chelly Amin, a meteorologist with the service.

“It’s definitely going to be a really horrible situation here come sunrise in the morning in those areas,” Amin said.

A tornado was also reported on the ground near Harrisburg, Arkansas, in the evening.

The Arkansas Division of Emergency Management reported that there was damage in 22 counties due to tornadoes, wind gusts, hail and flash flooding. At least four people were injured, but there were no reports of fatalities as of Wednesday evening.

In Kentucky, a tornado touched down Wednesday night around Jeffersontown, a suburb of Louisville, passing the Interstate 64 and Interstate 265 interchange, according to the weather service.

Four people were injured in Kentucky when a church was hit by debris from a suspected tornado, according to Ballard County Emergency Management. One person was in critical condition, while the others have non-life-threatening injuries.

In Brownsburg, Indiana, where part of a warehouse collapsed, the police department told people to not travel through the city. Five semitrucks were blown over on Interstate 65 near Lowell, Indiana, state police reported.

In Pilot Grove, Missouri, several structures were damaged, cars flipped over and power poles were snapped, the state emergency management agency said. Minor injuries were reported, according to the Missouri State Highway Patrol.

Authorities in eastern Missouri were trying to determine whether it was a tornado that damaged buildings, overturned vehicles and tore down utility poles, tree limbs and business signs in the morning in and around the city of Nevada.

Another tornado touched down in the northeastern Oklahoma city of Owasso on Wednesday, according to the weather service. There were no immediate reports of injuries, but the twister heavily damaged the roofs of homes and knocked down power lines, trees, fences and sheds.

Power was knocked out to nearly 90,000 customers in Arkansas, Mississippi, Missouri, Illinois, Kentucky and Tennessee, according to PowerOutage.us, which tracks outages nationwide. As storms moved through Indiana on Wednesday night, more than 182,000 customers lost power.

Strong and long-lasting tornadoes are possible in highest-risk area

About 2.5 million people were in a rarely called “high-risk” zone, covering parts of west Tennessee including Memphis; northeast Arkansas; the southeast corner of Missouri; and parts of western Kentucky and southern Illinois.

The Storm Prediction Center said “multiple long-track EF3+ tornadoes” were likely. Tornadoes of that magnitude are among the strongest in intensity.

At a slightly lower risk for severe weather was an area that included Chicago, Indianapolis, St. Louis and Louisville, Kentucky. Dallas, Detroit, Milwaukee and Nashville, Tennessee, were also at risk.

Floods could inundate towns, sweep cars away

A line of thunderstorms dropped heavy rain through parts of Indiana on Wednesday night. At least one street was flooded in Indianapolis, with water nearly reaching the windows of several cars, according to the city’s metropolitan police department. No one was in the vehicles.

Additional rounds of heavy rain were expected in parts of Texas, the lower Mississippi Valley and the Ohio Valley from midweek through Saturday. Forecasters warned that they could track over the same areas repeatedly, producing dangerous flash floods capable of sweeping cars away.

Middle Tennessee was looking at severe storms followed by four days of heavy rains as the front stalls out and sticks around through the weekend, according to NWS meteorologist Mark Rose.

“I don’t recall ever seeing one like this, and I’ve been here 30 years,” Rose said. “It’s not moving.”

Rain totaling up to 15 inches (38 centimeters) was forecast over the next seven days in northeastern Arkansas, the southeast corner of Missouri, western Kentucky and southern parts of Illinois and Indiana, the weather service warned, with some areas in Kentucky and Indiana at an especially high risk for flooding.

Power outages in Upper Midwest

In Michigan, crews worked to restore power after a weekend ice storm. More than 122,000 customers were still without electricity on Wednesday, according to PowerOutage.us.

The Mackinac Bridge connecting Michigan’s Lower and Upper Peninsulas was shut down because large chunks of ice were falling from cables and towers. It was the third consecutive day of bridge interruptions from the ice storm.

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Associated Press writers Andrew DeMillo in Little Rock, Arkansas; Adrian Sainz in Memphis, Tennessee; Seth Borenstein in Washington; Isabella O’Malley in Philadelphia; and Ed White in Detroit.