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.

Meanwhile, the severe weather threat will linger through Sunday from Florida northward into the upper Ohio River Valley, forecasters warned.

A destructive wave of storms swept into Alabama on Saturday, bringing with them a rarely-seen threat level for possible long-track tornadoes, winds of up to 70 m.p.h., golf ball-sized hail and torrential rain.