A major storm is bearing down on Tennessee, Alabama and Mississippi, where “violent,” “long-track” tornadoes are possible on Thursday.

“Violent” means tornado winds could be 166 mph or greater, with ratings of EF-4 or EF-5. These tornadoes are often “long-track,” which means they could be on the ground for at least 25 miles.

So far, this storm system has already produced a tornado in central Texas and three dozen reports of huge, damaging hail. Now it’s moving into the Ohio and Tennessee River Valleys with a trailing cold front stretching to the Gulf Coast.

Ahead of this storm, supercell thunderstorms are expected to break out Thursday afternoon and evening from Mississippi to Kentucky, with damaging winds, violent tornadoes and baseball-sized hail.

The National Oceanic and Atmospheric Administration’s Storm Prediction Center issued a “high risk” warning for severe weather in Tennessee, Alabama and Mississippi.

Alabama Gov. Kay Ivey has issued a state of emergency for 46 counties, while in Mississippi, more than two dozen people have taken shelter at an elementary school in Lowndes County ahead of the severe weather. Two other schools, each of which can hold about 400 people, also are open as shelters, the Lowndes County emergency management director told ABC News.

All shelters are providing hand sanitizer and masks, enforcing social distancing and checking people’s temperatures.

ABC News’ Elwyn Lopez contributed to this report.