Washington DC - A colossal US winter storm is brewing, with meteorologists on Saturday warning of deep snowfalls, frigid temperatures, and ice-covered roads as millions of Americans brace for treacherous conditions.

More than 55 million people are in the path of the dangerous storm set to plunge the eastern half of the US into a deep freeze through Monday, with the National Weather Service (NWS) warning of blizzard conditions in states from the central plains to the Mid-Atlantic.

Winter storm warnings or advisories have been issued from Montana, in the country's Rocky Mountain northwest, clear across to the coastal states of Maryland, Delaware, and Virginia.

Parts of the eastern states of New York and Pennsylvania are facing "heavy lake-effect snow" coming off the Great Lakes which could dump as much as two feet of snow on the region, according to the NWS.

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Forecast company AccuWeather said Saturday that the lake-effect snow total in the region, already blanketed in snow in the first week of 2025, could even top four feet.

A blizzard will rage across the Central Plains by early Sunday, and "whiteout conditions will make travel extremely hazardous, with impassable roads and a high risk of motorists becoming stranded," the NWS said.

Temperatures could sink to below zero Fahrenheit in some states, while strong wind gusts will compound the dangers, it added.

From Kansas to Missouri and Ohio, up to 12 inches of snowfall is expected by Sunday. "For some, this could be the heaviest snowfall in over a decade," according to NWS.

The US capital Washington could be blanketed in five inches or more of snow, with up to 10 inches possible in nearby areas.

With the jet stream diving southward, temperatures are expected to plunge, bringing the mercury tens of degrees below seasonal norms down to the US Gulf Coast.

Another major concern is freezing rain and sleet expected from Kansas eastward to West Virginia and Virginia, setting the stage for thick ice to coat roads, making travel hazardous, bringing down trees and electricity lines, and potentially leaving millions of customers without power during a cold snap.

The governors of Missouri and Virginia have declared a state of emergency in their states, and they took to social media to warn residents to expect hazardous weather this weekend.

Conditions could prove especially perilous in the Appalachian Mountains, where a deadly hurricane in late September devastated communities and ravaged multiple southeastern states including Kentucky.

The storm "will likely cause significant disruption and dangerous conditions on our roads and could cause significant power outages just 24 hours or so before it's going to get really cold in Kentucky," Governor Andy Beshear told an emergency meeting.