Two major winter storms thrashing the western two-thirds of the United States on Wednesday appeared set to disrupt travel plans of millions of Americans headed to Thanksgiving Day destinations on jam-packed highways and airplanes.

The first storm front was moving across the upper Midwest, where it was forecast to clobber parts of Iowa, Wisconsin and Minnesota with almost a foot of snow (30 cms) and wind gusts of up to 80 kilometers per hour, making travel difficult if not impossible, the National Weather Service (NWS) said.

It also warned of possible winds of up to 95 kph and rainstorms across a wide swath of the central US from western Texas up through Missouri and into Ohio on Wednesday, as millions will hit the roads and board airplanes for the holiday.

The treacherous weather jeopardized travel plans for some of the 55 million Americans expected to fly or drive at least 80 kms from their homes for Thursday's Thanksgiving holiday, according to the American Automobile Association.

"It's a real bummer," said Ally Lytle, a 20-year-old student at the University of Wyoming in Laramie, who will be unable to make a 645-km road trip home to Jackson Hole after the storm swept through the area on Tuesday.

The storm had already closed highways across the region and canceled and delayed hundreds of flights in and out of Denver on Tuesday.

Wind gusts of more than 65 kph on the East Coast on Thursday may also ground the giant balloons featured during the Macy's Thanksgiving Day Parade in New York City, the weather service said in an advisory.

"Look, I know this weather means people won’t get to see their families, might be stranded in airports, etc, and all of that is awful," said Susan Arendt on Twitter. "But I’ll be really sad if the wind means no balloons in the Macy’s parade."

The second storm was rapidly intensifying as it pushed toward Oregon and northern California, where damaging winds, coastal flooding and heavy mountain snows of up to 120 cm were forecast, the NWS said.

The front was also expected to dump heavy rain, threatening flash floods across southern California, from San Diego to Los Angeles, the weather service said.