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-setting 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.

“I don’t really know how to explain it,” said Cody Ferguson, who hid in a storm shelter with neighbors while the twister roared above them. “Just real loud rumbling, a lot of bangs, debris.”

His home that he built from the ground up was demolished, and he said a neighbor across the street was seriously injured.

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 powerlines in Indiana.

Forecasters on Thursday warned 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.

The bullseye was centered on a swath along the Mississippi River and includes the more than 1.3 million people around Memphis, Tennessee.

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

Round after round of heavy rains are expected in the central U.S. through Saturday and could produce dangerous flash floods capable of sweeping away cars. The potent storm system will bring “significant, life-threatening flash flooding” each day, the National Weather Service said.

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 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.

There already were some water rescues on Thursday in flooded parts of Nashville, Tennessee, where the rain could persist for days after an unnerving night of tornado warnings that drained the batteries of some sirens across the city, the fire department said.

Western Kentucky residents were bracing for historic amounts of rain and flooding in places that normally don’t get overwhelmed by water, Gov. Andy Beshear said.

Flash flooding is particularly worrisome in rural areas of the state, where floodwaters can quickly rush off the mountains into the hollows. Less than four years ago, dozens died in flooding across eastern Kentucky.

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