Violent tornadoes ripped through parts of the U.S., wiping out schools and toppling semitractor-trailers in several states.

Millions of Americans across the country are on alert for a severe weather outbreak as violent, long-track tornadoes with damaging winds of up to 80 mph and large hail are expected across the Midwest and South with the cross-country storm moveing east.

"Get to the sturdiest structure you have access to and remain in place until the storms pass," the NWS told residents in Alabama on Saturday night, when multiple tornado warnings were issued. At least 250,