Holiday travel likely to be troublesome throughout the nation due to of weather

It'll be a white Christmas for the northern Plains and some Western states, but it's likely to cause troublesome travel.

Forecasters cautioned drivers to keep alternate routes in mind and prepare for possible delays.

Southern California even got a dose of snow, with about 2 inches falling in a mountainous region about 75 miles north of Los Angeles. It shut down the state's main north-south interstate — I-5 — for nearly four hours Saturday.

In Arizona, parts of Interstate 40 and other highways in the state's high country were closed after winter weather hit, leading to multiple crashes. A winter storm warning was issued for much of northern Arizona for elevations above 6,000 feet until late Saturday or early Sunday morning, depending on locations.

In the coming days, a large swath of the Dakotas is under a blizzard warning, with the National Weather Service forecasting heavy snow and strong winds Sunday and Monday. The Dakota Access pipeline protest encampment in southern North Dakota will be affected. Though many left during a blizzard earlier this month, Morton County Sheriff's Department spokesman Rob Keller said, there could be at least 500 people still at the camp.

To the east, parts of central Minnesota are under an ice storm warning. To the west, snow is also forecast for much of Idaho, Montana, Utah and northeast Colorado.

Air travel wasn't yet impacted Saturday at the nation's major airports. But snowy conditions Friday in Appleton, Wisconsin, caused the Minnesota Vikings' team plane to slide off a runway.

The Storm Prediction Center cautioned that warm, humid air could cause severe weather in the lower Plains, Arkansas and Oklahoma on Sunday.