Powerful winter storms lashed the United States on Wednesday, with heavy snow snarling travel across wide areas, even as unusual warmth was expected in others.

Blizzards forecast to dump up to two feet (60 centimeters) of snow swept across a vast band of the country from the West Coast to the Great Lakes, grounding flights and knocking out power to tens of thousands.

Warnings of heavy snowfall were even issued for usually sunny areas near Los Angeles, as well as for more typical winter weather spots in the far north.

Forecasters with the National Weather Service said two rounds of snow would wallop parts of Minnesota in a "historic winter storm (that) will likely lead to impossible travel."

"Heavy snow will combine with northeast wind gusts of 35 to 45 mph (55 to 70 kph)... This will lead to significant blowing and drifting snow with whiteout conditions in open areas. Some drifts may be several feet deep," a warning said.

"If you must travel, keep an extra flashlight, food, and water in your vehicle in case of an emergency. Travel should be restricted to emergencies only. If you must travel, have a winter survival kit with you. If you get stranded, stay with your vehicle."

More than 1,550 flights within, into or out of the United States had been cancelled by 0000 GMT Thursday, according to Flightaware.com, with its "Misery Map" showing Denver, Salt Lake City and Minneapolis-St Paul particularly badly hit.

Roads were also difficult, with Wyoming suffering from problems even on main highways.

"Please change travel plans if you are coming towards Wyoming," the state's department of transport posted on its Facebook page. "A major winter storm and multiday closures are likely on Interstates and secondary roads throughout Wyoming!"

Around 280,000 properties were without power across the country, according to Poweroutage.us, almost half of them in Michigan, where snow, sleet and freezing rain were icing power lines, making them vulnerable to gusting winds.

'COLD AND DANGEROUS'

An unusual blizzard warning was put in place for the mountains around Los Angeles from early Thursday, with snow expected to fall even at relatively low elevations.

"Now is the time to prepare for a COLD AND DANGEROUS winter storm expected for much of the week," the NWS in Los Angeles warned.

"Several FEET of snow is expected in the mountains with a few inches possible as low as 1000 feet. Gusty and potentially damaging winds are also expected."

While not everyone was expected to wake up to a whiteout, even people in Los Angeles will be treated to the sight of snow-dusted mountains.

"Nearly entire population of (California) will be able to see snow from some vantage point later this week if they look in right direction (i.e., toward highest hills in vicinity)," climate scientist Daniel Swain of UCLA tweeted.

It will be chilly by southern California standards, but forecasters warned that some areas of the country would be very cold, with parts of the northern and central plains seeing wind chills as low as -30 degrees Fahrenheit (-34 C).

But while the West and some northern parts of the United States are shivering, eastern areas will be unusually warm.

"These highs on Thursday will be particularly anomalous for the Ohio Valley and Mid-Atlantic, where temperatures 40+ degrees above average will feel more like June than February," the NWS said.

© Agence France-Presse