LAKE CITY, Ark. — Tornadoes and violent winds flattened homes and ripped apart buildings from Oklahoma to Indiana in the first round of lingering storms that are expected to bring record rains and life-threatening flash floods across the nation’s midsection in the coming days.

At least six people were killed in western Tennessee, Missouri and Indiana in the first wave on Wednesday and early Thursday that spawned powerful tornadoes — one launching light debris nearly 5 miles above the ground in Arkansas.

Workers on bulldozers cleared rubble along the highway that crosses through Lake City, Arkansas, where a tornado sheared the roofs off homes, collapsed brick walls and tossed cars into trees.

Those killed included a man and his teenage daughter whose home was destroyed in western Tennessee, and a man who died after his pickup struck downed power lines in Indiana.

Forecasters warned Thursday of catastrophic weather soon ahead. Satellite imagery showed thunderstorms lining up like freight trains — taking the same tracks over communities in Arkansas, Tennessee and Kentucky, according to the national Weather Prediction Center in Maryland.

More than 90 million people were at risk of severe weather — from Texas to Minnesota to Maine, according to the Oklahoma-based Storm Prediction Center.

With more than a foot of rain possible over the next four days, the prolonged deluge “happens once in a generation to once in a lifetime,” the National Weather Service said. “Historic rainfall totals and impacts are possible.”

Water rescue teams and sandbagging operations were being staged across the region, and the Federal Emergency Management Agency was ready to distribute food, water, cots, generators and meals.

Forecasters attributed the violent weather to higher temperatures, an unstable atmosphere, strong wind shear and abundant moisture streaming from the Gulf.

The Arkansas Division of Emergency Management reported damage in 22 counties caused by tornadoes, wind gusts, hail and flash flooding.

In far western Kentucky, four people were injured while taking shelter in a vehicle under a church carport, the emergency management office in Ballard County said.

Emergency crews worked for several hours to free a warehouse worker trapped after a roof and a wall collapsed near Indianapolis.

The woman was conscious and talking throughout the effort Wednesday.

Wind gusts blew over semitrucks, downed power lines and caused power outages that disrupted classes in at least 10 school districts in Indiana.

More than half a million customers in Indiana, Ohio, Kentucky, Arkansas, Tennessee, West Virginia, Mississippi, Missouri and Texas were without power early Thursday following the peak of the storms, according to PowerOutage.us.