"Some tornadoes could be long-lasting, adding to the danger, especially for those that occur after dark." The storm is expected to bring severe thunderstorms to the East Coast on Sunday,

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.

At least 30 people died as violent weather swept the country on Friday and Saturday, and the threat isn't over.