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.

Let us break it all down for you.

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Winter weather is lashing the West

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.

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This is the same system that brought heavy rain to California on Monday. As it continues eastward, it is expected to develop into a significant winter storm across portions of Colorado and Utah.

Winter storm warnings are in effect across the region as snow depths of up to 3 feet are expected at the highest elevations.

Travel over mountain passes is expected to become extremely difficult, if not impossible, as Thanksgiving approaches.

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

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Rain and snow are rolling through the east

Millions of people in the eastern half of the US are also taking part in the campaign and should be patient as travel delays are expected before Thanksgiving on Tuesday.

The FOX Forecast Center said a cold front stretching from the southeast into northern New England is producing rain, snow, freezing rain and even rumbles of thunder in some places.

Major airports in the East are likely to experience disruption due to the large number of people traveling, poor weather and low ceilings. Poor visibility and gusty winds will be a problem as the system slides off the East Coast.

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Farther north, where temperatures were colder, freezing rain threatened to make travel in New England dangerous for those heading to parts of Vermont, New Hampshire and Maine.

The good news is that temperatures will rise again throughout the day and the ice will begin to melt.

Severe weather is unlikely in the Southeast, but rain and possible thunderstorms could cause delays at the world’s busiest airport – Hartsfield-Jackson Atlanta International Airport.

The majority of the rain and thunderstorms will ease Tuesday night.

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Thanksgiving winter storm

As if the pre-Thanksgiving travel woes weren’t enough, the FOX Forecast Center is also 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 starting their trips back home.

This is all due to the winter storm currently sweeping across the West. By 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.

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For those of you driving on Thanksgiving, expect delays on the roads and at airports.

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.

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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.

Cities in New York, such as Syracuse, buffalo and Binghamton are also likely to get caught up in the accumulating snowfall.