A Tornado Warning was issued in parts of Northern California Monday afternoon.• Video Above: Tornado Watch vs. Tornado Warning At around 3:14 p.m., a severe thunderstorm

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

A new tornado watch was issued Sunday for parts of West Virginia, Ohio and PA. 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.