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US winter storm to bring blizzard, tornadoes and floods
"This one is a little larger than your average winter storm," says a meteorologist of the wintry system.
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A coast-to-coast storm is bringing heavy snowfall, powerful winds, the threat of thunderstorms and other extreme weather across the US.
Some western states, including Montana, Wyoming and South Dakota, are expecting up to 2ft (60cm) of snow.
Other states in the south, meanwhile, are facing a potential tornado outbreak.
The storm could affect millions of residents in nearly every state in the contiguous US, experts said.
"It's a fairly vigorous storm system," said Rich Otto, a meteorologist with the Weather Prediction Center. "This one is a little larger than your average winter storm."
The worst of the weather was expected to hit on Monday night and into Tuesday, bringing gusty winds over 40mph (64km/h) and heavy snowfall to the central and northern High Plains, a region of the US that includes eastern Montana, Wyoming, South Dakota and Nebraska, Mr Otto said.
Blizzard warnings from the National Weather Service are in effect for all of those states, as well as Colorado. Those are triggered by winds of at least 35mph accompanied by heavy snowfall.
Winter storm alerts are also in effect for over 15 million people living in more than a dozen states across the country.
Heavy snowfall combined with strong wind gusts will create low visibility and "treacherous" travel conditions, Mr Otto said. "Folks should stay home during the day [on Tuesday] if they live up north," he said.
The storm could also dump a quarter to half an inch of freezing rain on some Midwestern states, while southern states face the possibility of severe thunderstorms, hail, flash floods and even a couple of strong tornadoes, according to the Storm Prediction Center.
The extreme weather is expected to linger through much of this week, experts said.
The storm system began to hit the US last Friday, bringing powerful winds to California.
The Sierra Nevada mountain range in northern California reported 5ft of snow in some areas over the weekend, forcing some highways to close and triggering avalanche warnings in the area through Monday night.