Millions of Thanksgiving travelers in states across the US could see their holiday plans hit by a pair of storms sweeping through the country.

A strong storm was expected to drop up to a foot of snow in parts of Colorado and Wyoming on Tuesday, prompting airlines to announce travel alerts and the National Weather Service (NWS) to issue blizzard and wintry weather warnings from the Rocky Mountains to the Great Lakes.

The weather front will work its way to the east coast by Thursday, the NWS said, bringing up to a foot of snow northern Maine. The effects will be felt across New England and as far down as New York City, where strong winds could threaten the city’s Thanksgiving Day parade.

Another storm was strengthening rapidly in the north west on Tuesday, and is expected to work its way from south-west Oregon to north-west California. That storm is likely to bring “damaging winds, heavy mountain snows [and] coastal flooding”, the NWS said, while further south LA and San Diego could see heavy rain and be subject to flash flooding.

About a quarter of Denver international airport’s 1,500 flights were canceled on Tuesday morning, and airport officials said more cancellations were likely.

“There’s still a lot of uncertainty with this storm,” said spokeswoman Emily Williams.

The storm was expected to move into the Plains later in the day, bringing high winds and more snow to Minnesota, Wisconsin and upper Michigan. It could bring another round of snow to the upper midwest from Thursday through Saturday, and a chance of snow this weekend in interior New England, said Alex Lamers, an NWS meteorologist.

“That could be a coast-to-coast storm,” he said.

The Minneapolis-St Paul metropolitan area could see its biggest November snowfall in nearly a decade, and travel in north-western Wisconsin “is going to be chaotic”, said another NWS meteorologist, Brent Hewett.

The Minneapolis airport could be hit but Chicago, with its two big airports, should only see rain from the storm, NWS officials said.

The storm could also bring disappointment for fans of the huge balloons flown at Macy’s Thanksgiving Day Parade in New York City.

Organizers were preparing to ground the famous inflatables, given forecast 40-50mph gusts. Rules put in place after several people were injured by a balloon years ago require lower altitudes or full removal if sustained winds exceed 23mph and gusts exceed 34mph. The decision will be made on parade day.

The second storm, brewing in the Pacific, was expected to hit the west coast on Tuesday afternoon or evening, bringing snow to the mountains and wind and rain along the coasts of California and Oregon.

Dangerous winds on Monday flipped a tractor-trailer, downed power lines and temporarily closed a stretch of US Highway 6 south of Yosemite national park near Bishop, California.

This month, the American Automobile Association predicted that the number of travelers over a five-day stretch starting on Wednesday will be the second-highest ever, behind 2005, despite rising costs for road trips.

Airlines expect traffic to be up about 4% on last year and have added about 850 flights and 108,000 seats per day on average to handle the increase, according to the trade group Airlines for America.

Airline travel before Thanksgiving tends to be spread out over several days, but most people want to go home on the Sunday or Monday after the holiday.