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.

The National Weather Service predicted extreme weather across a vast swath of the U.S. with a population exceeding 100 million people. Powerful winds gusting up to 80 mph were forecast from the Canadian border to Texas.

The storm system is expected to bring rain to California’s central coast Friday, a day after the National Weather Service confirmed a tornado touched down in East Los Angeles as a large strong storm system caused flooding in the area.

Forecasters say the severe storm threat will continue into the weekend, with a high chance of tornadoes and damaging winds Saturday in Mississippi and Alabama. Heavy rain could bring flash flooding to some parts of the East Coast on Sunday.

Experts say it’s not unusual to see such weather extremes in March, with storm systems producing heavy snow and blizzards on the cold side and severe thunderstorms and tornadoes on the warm side.

“What’s unique about this one is its large size and intensity,” said Bill Bunting of the weather service’s Storm Prediction Center in Norman, Oklahoma. “And so what that is doing is producing really substantial impacts over a very large area.”

The Storm Prediction Center said fast-moving storms could spawn tornadoes and hail up to baseball-size on Friday. But the greatest threat would come from straight-line winds near or exceeding hurricane force, with some gusts possibly reaching 100 mph.

Forecasters said areas most at risk were in eastern Missouri, much of Illinois and portions of Iowa, Kentucky, Tennessee, Arkansas and Mississippi. About 47 million people faced an enhanced to moderate severe storm threat from Madison, Wisconsin, to Birmingham, Alabama.

Forecasters grew increasingly worried that intense thunderstorms further south will likely bring an even greater tornado threat.

The Storm Prediction Center said parts of Mississippi including Jackson and Hattiesburg and areas of Alabama including Birmingham and Tuscaloosa will be at a high risk of damaging winds and tornadoes. A moderate threat extends into eastern Louisiana, western Georgia and the western Florida Panhandle.

“We fear we could see intense, destructive tornadoes over the South tomorrow,” Bunting said.

Alabama Gov. Kay Ivey declared a preemptive state of emergency Friday, urging people across the state to be vigilant overnight and into the weekend.

Forecasters warned that heavy snow whipped by powerful winds are likely to make travel treacherous in parts of the Rockies and Northern Plains. Blizzard conditions were possible in the Dakotas and Minnesota.

Winter storm warnings issued Thursday lingered into Friday morning in mountainous regions of Arizona and Utah, where more than a foot of snowfall was possible. Forecasters warned of poor visibility and icy road conditions. Snow in northern Arizona shut down some stretches of Interstate 40.

The winter blast continued after snowfall of up to 3 feet blanketed the Sierra Nevada earlier in the week.

Warm, dry weather and sustained winds of up to 45 mph brought what the weather service called “near historic” conditions for sparking wildfires Friday to the Southern Plains and parts of the Southwest. Wind gusts exceeding 80 mph were possible.

Forecasters also warned about an extreme risk of fires in parts of northern Texas, much of Oklahoma and southeast Kansas. A broader area where the fire threat was designated as critical stretched from eastern New Mexico into Texas and north to a portion of southern Iowa.