A cross-country storm will explode in strength as it moves over the central United States Friday, delivering extreme weather to millions through the weekend, including the chance of multiple strong tornadoes.

Dangerous weather conditions will peak Saturday, with one of the most prolific tornado-producing setups in years expected to develop over the Deep South — with disastrous results likely.

AccuWeather's Jon Porter warns of a triple threat facing the central U.S., which include fire danger in the South, blizzards in the North and damaging winds and tornadoes in the heart of the nation.

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.

On Thursday, the storm was bringing heavy snow and strong winds to the Sierra Nevada and heavy rainfall over parts of coastal southern California.