Cities at risk include the tornado-ravaged Nashville area.

Large hail and damaging wind gusts are also possible.

The area at risk stretches all the way from central Arkansas to southern Ohio.

An outbreak of severe weather, including the threat for "significant tornadoes," is forecast for portions of the central and southern U.S. on Thursday during the evening and overnight, forecasters warned.

Cities at risk include the tornado-ravaged Nashville area, which is still reeling from a violent outbreak just over a week ago. Other metro areas where severe weather is possible include St. Louis, Louisville and Memphis, the Storm Prediction Center said.

"Significant/EF2+ rated tornadoes may occur," the prediction center said.

A tornado watch was hoisted Thursday afternoon for portions of Kentucky, Tennessee, Missouri, Illinois and Indiana. This means conditions are favorable for tornadoes to form. Nashville is in the tornado watch area.

In addition to the threat of tornadoes, all modes of severe weather will be possible as the thunderstorms erupt, including large hail and damaging wind gusts, AccuWeather warned.

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The area at risk stretches all the way from central Arkansas to southern Ohio.

While storms should start to fire up during the day in some areas, "thunderstorms may not arrive in cities such as Memphis and Nashville until after nightfall," AccuWeather said.

The storms that ravaged the Nashville area last week happened at night, killing 25 people, many as they slept. "We have big concerns about the threat of nighttime tornadoes," the National Weather Service in Nashville said. "Now is the time to make sure your NOAA Weather Radio is operational and that you have a second way to get your warnings."

The storm system will clear out of the mid-South and Ohio Valley by Friday morning, AccuWeather said.

Also on Thursday, heavy rainfall and the potential of flash flooding from a separate storm system will continue from southern California into the Southwest, the National Weather Service said. Over 12 million people were under a flash flood watch Thursday in the Southwest, including the entire Phoenix metro area.

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Contributing: The Tennessean