NEW YORK – As millions head home for the Christmas holidays, they will face wet conditions at the end of the week, with rain and thunderstorms expected across much of the country.

Meanwhile, snow levels are falling in the West as more storms hit the coast, bringing heavy rains that could lead to flooding in some places.

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Constant rain and storms drenching the south

The storm is expected to bring the first round of rain and thunderstorms to the south on Christmas Eve and Christmas Day before quickly dissipating on Thursday. But immediately afterward, a new storm will move from the Rocky Mountains into the southern Plains, bringing with it a new round of rain and thunderstorms, according to the FOX Forecast Center.

This will begin across Texas and Oklahoma, where thunderstorms will break out throughout the day on Thursday, potentially impacting travel, particularly at Dallas Fort Worth International Airport.

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These storms can be severe, particularly in the afternoon, with damaging winds and a few tornadoes being the main threat. This is not expected to be a repeat of December 26, 2015, when 12 tornadoes, including an EF-4, ripped through North Texas.

Storms return to the Ark-LA-Tex region Thursday evening, bringing rainy weather for the third straight day. Flash flooding is possible as heavy rain is likely to fall at a rate of up to 2.5 centimeters per hour in the same areas that received rain on Tuesday and Wednesday.

According to the FOX Forecast Center, precipitation amounts will increase significantly on Friday and Saturday, just in time for the busiest travel days of the post-holiday period.

Rain is expected to fall from the Gulf Coast to the Great Lakes. According to the FOX Forecast Center, details on this part of the forecast will become clearer as the week progresses.

Storm after storm is moving across the west coast

A line of storms will move from the Pacific and through the Northwest through Saturday. By this weekend, seven different systems will have impacted the Northwest with atmospheric rivers of varying strength.

Western Washington, Oregon and Northern California will see more than a foot of rain. Up in the mountains, more than seven feet of snow could fall along the higher peaks of the Cascades.

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The first storm came last Friday. The fifth storm is expected on Christmas Day. The sixth system will move in Thursday evening, followed by No. 7, which will hit the Northwest starting Saturday.

At lower elevations, the cumulative impact of repeated rainfall will increase flooding concerns throughout the week. Only minor flooding is currently expected in urban areas, small streams and even some rivers.

The same weather conditions in California will also bring rain to Washington and Oregon, particularly west of the Cascades. The heaviest rain is expected from Wednesday to Friday, when the impact is expected to be greatest.

Snowfall levels Wednesday evening and beyond will be colder than earlier in the week, and snow should really pile up in the Cascades, Sierra Nevada, Bitterroots, Sawtooth, Boise, Absaroka, Lewis and Teton Mountains.

Snow levels will drop below 3,000 feet, allowing large amounts of snow to accumulate in the Cascade Passes. Motorists heading home after Christmas must expect potentially treacherous road conditions as snow piles up.