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 moving 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,

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

A sprawling storm system crossing the U.S. caused deadly crashes, overturned semitrucks and fanned dozens of wildfires in several central states, prompting evacuation orders in some communities.