By JEFF MARTIN

Forecasters are warning of potentially deadly flash flooding and strong tornadoes as more rounds of thunderstorms are poised to strike parts of the Midwest and South.

The potent storm system will bring the threat of “significant, life-threatening flash flooding” starting Wednesday, according to the Weather Prediction Center, a part of the National Weather Service.

The new flood threat also comes as residents in parts of Michigan continue to dig out from a weekend ice storm.

Floods could inundate towns, sweep cars away

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

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

Rain totaling up to 15 inches is 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.

Rainfall could be a once-in-a-quarter-century event

“We’re potentially looking at about two months of rain in just a handful of days,” said Thomas Jones, a meteorologist at the National Weather Service in Little Rock, Arkansas.

Little Rock’s monthly average rainfall for March is just under 5 inches. The rainfall that eastern and northeastern Arkansas could see is something only expected once every 25 to 50 years.

The copious amount of rain in the forecast is rare, Jones said, and moisture from the Gulf is boosting the amount of precipitation the thunderstorms could release.

Strong tornadoes could slam the Midwest on Tuesday

Storms could spin up tornadoes in Oklahoma, Kansas and Missouri on Tuesday, forecasters said.

The National Weather Service’s Storm Prediction Center in Norman, Oklahoma, said intense thunderstorms, including a few supercells, are possible Tuesday evening and overnight from central and southern Oklahoma up into central Kansas and western Missouri.

The primary risks are for very large hail — 2 inches (5 centimeters) in diameter or greater — as well as a few tornadoes, some of which could be strong, and severe wind gusts. The area at greatest risk for a strong tornado includes Oklahoma City, and the Kansas cities of Wichita and Topeka. The risk of large hail extends from Fort Worth, Texas, to Kansas City.

43 million people at risk for severe weather on Wednesday

On Wednesday, a large swath of the nation from northeast Texas to Michigan will see the potential for high winds and tornadoes. The area at highest risk for severe weather includes 43 million people and many of the nation’s largest cities. including Chicago, Indianapolis, St. Louis and Memphis, Tennessee.

Dallas, Detroit, Milwaukee, and Nashville, Tennessee, will also be at risk for severe storms on Wednesday.

Earthquake center prepared for floodings

The heaviest rains are forecast to fall in the New Madrid Seismic Zone, where researchers constantly monitor earthquake activity in the nation’s most active area for earthquakes east of the Rocky Mountains. Centered in southeast Missouri, the seismic zone extends to several nearby states, including Arkansas and Tennessee. It’s famous for a series of powerful earthquakes in 1811 and 1812 that were felt in a large part of the Midwest and South. Experts say another devastating earthquake in the zone is possible.

Scientists have learned lessons from Mississippi River flooding to be vigilant about where they locate monitoring equipment, said Mitch Withers, a research professor at the Center for Earthquake Research and Information at the University of Memphis. About 70 stations in the area should be protected from flooding, and “we’ll still be getting our data and monitoring for earthquakes,” he said.

Wintry mix blasts Upper Midwest

In Michigan, crews were trying to restore power Tuesday after a weekend ice storm toppled trees and power poles. Nearly 200,000 customers were without power in Michigan, plus another 25,000 in Wisconsin, according to PowerOutage.us, which tracks outages nationwide.

In the mitten-shaped Lower Peninsula of Michigan, schools in several counties were closed for a second day on Tuesday. Sheriff’s deputies used chain saws to clear roads. Drivers waited at gas stations in lines that stretched for blocks.

More wintry precipitation is in store for the region: A mix of sleet and freezing rain could keep roads treacherous Tuesday night into Wednesday across parts of Michigan and Wisconsin, the weather service said.

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

Associated Press Writers Isabella O’Malley in Philadelphia; Ed White in Detroit; and Steve Karnowski in Minneapolis contributed.