Millions of Americans in the U.S. began filling the streets and airports ahead of Thanksgiving, but a powerful storm moving from coast to coast could complicate travel ahead of the holiday and as people begin their journey home after being with family and friends celebrated.

The first half of the busy Thanksgiving travel week will see storms dumping rain and mountain snow in the West, while the eastern half of the country will experience rain, freezing rain and snow.

As if that wasn’t enough to dampen the holiday spirit, the FOX Forecast Center is watching another winter storm that could significantly impact travel in the Northeast as millions of people prepare to head home.

The FOX Forecast Center said the latest in a line of low pressure systems is moving across the West Coast and into the Rocky Mountains, bringing wintry weather and rain to the region.

A severe winter storm will bring heavy snowfall to parts of Colorado and Utah.

Winter storm warnings are in effect across the region as snow depths of up to 3 feet (90 cm) are expected at the highest elevations, making crossing mountain passes extremely difficult, if not impossible.

Rainfall could occur in Salt Lake City, Las Vegas and Denver through Wednesday.

However, the FOX Forecast Center does not currently expect any major impacts in Denver.

A winter weather advisory covers the Mile High City as variable snowfall of up to 2 to 4 inches occurs in places Wednesday morning, potentially complicating the morning commute.

Conditions could worsen on major highways such as Interstate 25 and Interstate 70 before the system leaves the region before Thanksgiving Day.

Winds caused temperatures to drop to as low as 20°C across the Great Lakes. Places like north-central Wisconsin may see some snow on Thanksgiving.

The winter storm intensifies to the east just in time for last-minute Thanksgiving travel

As if the pre-Thanksgiving travel woes weren’t enough, the FOX Forecast Center is watching another winter storm on Thanksgiving Day, which is expected to delay last-minute holiday trips as well as those shopping on Black Friday or making their way back home.

This is all due to the winter storm devastating the West. On Wednesday the weather looks calm in the East, but on Thursday the system will move through the Midwest and Ohio Valley into the Northeast.

The FOX Forecast Center expects a line of rain and thunderstorms to move through the Southeast and Tennessee Valley on Thursday.

Some of these storms could become severe and produce devastating gusts of wind.

To the north, heavier rain is expected in parts of the Mid-Atlantic and Northeast through Thursday night.

The FOX Forecast Center said the system will strengthen as it approaches the region, and winds could also increase, causing delays at airports in Washington, Baltimore, New York City and Philadelphia.

Snow will fall from the Midwest to New England north of the low pressure system.

Cold air will initially be limited as the system exits the Midwest, but as the low strengthens it will pull in colder air from Canada.

The FOX Forecast Center said snow totals are expected to be light, except for parts of the interior Northeast.

There could be heavier snow accumulation across the region, particularly at higher elevations.

Northern New York State, the Green Mountains of Vermont and the White Mountains of New Hampshire will likely see snow as the low moves offshore into Thursday night.

New York cities such as Syracuse, Buffalo and Binghamton are also likely to experience snowfall.

And as if heavy snow and storms weren’t enough to ruin the holidays, some of the season’s coldest air will enter the U.S. starting Thanksgiving and into early next month.

As the Thanksgiving winter storm leaves the Northeast, it will draw even colder, arctic air from Canada and spread south, possibly as far south as the Southeast.

By Friday, more than 230 million Americans will shiver in below-average temperatures.