A rare weather phenomenon that hasn't occurred since 1968 is expected to plunge temperatures across parts of the United States.

A significant change in the atmosphere means the weeks after Thanksgiving could be colder and snowier than normal across portions of the United States.

At 4:55 a.m. on Friday, the NWS Las Vegas NV released a winter weather advisory in effect until 8 a.m. for Eastern Sierra Slopes of Inyo County and White Mountains of Inyo County.

A winter storm warning is in effect for Alaska, while winter weather advisories span parts of Colorado, New Mexico, and Montana.

The cold snap has prompted several yellow weather warnings, along with a more severe amber warning in North Yorkshire.

The National Weather Service says scattered rain showers will begin Friday evening, with chances increasing after midnight Friday and early Saturday morning.

The slew of warnings and advisories comes as an atmospheric river moves out of the region after slamming the Golden State over the weekend. Another storm is approaching California from the northwest and is expected to bring heavy rain and mountain snow to much of the state beginning on Wednesday night and lasting through the end of the week.

The NWS Los Angeles/Oxnard CA issued a weather alert at 2:29 p.m. on Tuesday for strong thunderstorms until 3 p.m. The alert is for San Luis Obispo County Beaches, San Luis Obispo County Inland Central Coast and Santa Barbara County Inland Central Coast.