ATLANTA — Potentially deadly flash flooding, high-magnitude tornadoes and baseball-sized hail could hit parts of the Midwest and South on Wednesday as severe thunderstorms blowing eastward become supercharged, forecasters warned.

There were already tornado warnings Wednesday morning near the Missouri cities of Joplin and Columbia — merely the opening acts of what forecasters expect will be a more intense period of violent weather later Wednesday, as daytime heating combines with an unstable atmosphere, strong wind shear and abundant moisture streaming into the nation’s midsection from the Gulf.

The potent storm system will bring “significant, life-threatening flash flooding” starting Wednesday and continuing 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 in one of its flood warnings. “Historic rainfall totals and impacts are possible.”

The flood fears come as residents in parts of Michigan continued to dig out from a weekend ice storm.

Thunderstorms with multiple rounds of heavy rain were forecast in parts of Texas, the lower Mississippi Valley and the Ohio Valley beginning midweek and lasting through Saturday. Forecasters warned the storms could track over the same areas repeatedly and produce dangerous flash floods capable of sweeping cars away.

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.

“We’re potentially looking at about two months of rain in just a handful of days,” Thomas Jones, a weather service meteorologist in Little Rock, Arkansas, said Monday.

Parts of Arkansas, west Tennessee, western Kentucky and southern Indiana were at an especially high risk for flooding, the weather service said.

Parts of Tennessee could see 10 to 15 inches (25 to 38 centimeters) of rain through Saturday, said Krissy Hurley, meteorologist in charge of the weather service in Nashville. Hurley said the flooding could be “catastrophic” in some areas.

At least one tornado was spotted Tuesday night in Kansas. “Take cover now!” the weather service’s office in Wichita warned residents on the social platform X. No injuries were reported.

Another tornado touched down in the northeastern Oklahoma city of Owasso about 6:40 a.m. Wednesday, according to the weather service office in Tulsa. 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.

Tornado warnings were also issued in Missouri and Arkansas on Wednesday. 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 Wednesday morning in and around Nevada, Missouri.

The Missouri State Highway Patrol reported that the damage shut down a portion of U.S. Route 54 in the city of about 8,300 about 95 miles (153 kilometers) south of Kansas City, Missouri.

High winds with gusts of up to 50 mph (80 kph) were also expected across large parts of the Midwest. In Indiana, an extreme wind gust blew over five semitrucks on Interstate 65 near Lowell, state police reported. No one was hurt.

The ominous forecast comes nearly two years to the day that an EF-3 tornado struck Little Rock, Arkansas. No one was killed, but that twister caused major destruction to neighborhoods and businesses that are still being rebuilt today.

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

About 2.5 million people are in a rarely-called “high-risk” zone. That area most at risk of catastrophic weather on Wednesday includes parts of west Tennessee including Memphis; northeast Arkansas; the southeast corner of Missouri; and parts of western Kentucky and southern Illinois.

A tornado outbreak was expected Wednesday, and “multiple long-track EF3+ tornadoes, appear likely,” the Storm Prediction Center said. Tornadoes of that magnitude are among the strongest on the Enhanced Fujita scale, used to rate their intensity.

Hours before the storms were expected to arrive in the Memphis area and in eastern Arkansas, the weather service reported peak wind gusts of 58 mph (93 kph) in Memphis and 51 mph (82 kph) in Jonesboro, Arkansas.

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

In Michigan, crews worked to restore power after a weekend ice storm toppled trees and power poles. More than 135,000 customers in northern Michigan and 11,000 in northern Wisconsin were still without electricity Wednesday morning, according to PowerOutage.us, which tracks outages nationwide.

Schools in several counties in Michigan’s the mitten-shaped Lower Peninsula have been closed as deputies used chain saws to clear roads and drivers lined up at gas stations. And more wintry weather was on the way: A mix of sleet and freezing rain could keep roads treacherous into Wednesday across parts of Michigan and Wisconsin, the weather service said.

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

Heavy, wet snow also was forecast into Wednesday across the eastern Dakotas and parts of Minnesota.

Associated Press writers Andrew DeMillo in Little Rock, Arkansas; Sean Murphy in Oklahoma City; Adrian Sainz in Memphis; Isabella O’Malley in Philadelphia; Ed White in Detroit; Steve Karnowski in Minneapolis; and Hallie Golden in Seattle contributed.