A huge storm system crossing the U.S. threatens to unleash tornadoes Friday in the Mississippi Valley, blizzards in the northern Plains and dry, gusty conditions in Texas and Oklahoma that pose a high risk of wildfires.

Forecasters say a colossal storm could bring heavy winds, flooding, blizzard conditions and tornadoes to some parts of the country.

Numerous significant tornadoes are expected Saturday afternoon and evening, with the highest risk across several states in the Deep South, forecasters say.