California drivers warned to reconsider Christmas travel plans ahead of storms

California officials and weather forecasters urged holiday travelers to avoid the roads on Christmas Eve and Christmas Day ahead of a series of powerful winter storms that threatened to slam California with relentless rains, heavy winds and mountain snow through Friday.

Millions of people are expected to travel across the state. They will likely meet hazardous, if not impossible, traveling conditions as several atmospheric rivers were forecast to make their way through the state, the National Weather Service warned.

''If you're planning to be on the roads for the Christmas holidays, please reconsider your plans,'' said Ariel Cohen, a National Weather Service meteorologist in Los Angeles.

Forecasters said Southern California could see its wettest Christmas in years and warned about flash flooding, mudslides and debris flows in areas burned by last January's wildfires. County officials said Tuesday they were knocking on the doors of some 380 particularly vulnerable households to order them to leave.

Most areas saw scattered showers Tuesday morning, and the system was expected to pick up in the evening and intensify into Christmas Eve. Some regions will see rain and winds taper off Wednesday before another storm moves in.

Much of the Sacramento Valley and the San Francisco Bay Area were under a flood watch and a high wind warning through Friday. Forecasters warned of heavy snow and gusty winds for parts of the Sierra Nevada starting Tuesday that will create ''near white-out conditions'' and make it ''nearly impossible'' to travel through the mountain passes.

There's also a risk of severe thunderstorms and a small chance of tornadoes along the northern coast.

Southern California typically gets half an inch to 1 inch (1.3 to 2.5 centimeters) of rain this time of year, but this week many areas could see between 4 and 8 inches (10 to 20 centimeters), National Weather Service meteorologist Mike Wofford said. It could be even more in the mountains.

Potential widespread flooding, rockslides and mudslides are highly likely, especially in areas burned by last January's deadly Palisades fire, he added. Officials expect multiple road closures and airport delays during the storms. Downed trees and powerlines are also possible. Parts of Los Angeles were under evacuation warnings starting Tuesday.

The county had put up K-rails, a type of barrier, around the burn scar to help catch sliding debris during rainstorms. Residents could also pick up free sandbags to protect their homes, said Kathryn Barger, a Los Angeles County supervisor representing Altadena.

"When experts are projecting this type of rain in this short period of time, it's serious,'' Barger said.

Many people in burn scar areas decided not to leave after receiving the evacuation notification, Los Angeles Police Department Chief Jim McDonnell said Tuesday. He urged them to reconsider.

Local and state officials are gearing up to respond to emergencies through the week. The state has deployed resources and first responders to a number of counties along the coast and in Southern California ahead of the storms. The California National Guard is also on standby to assist.

An atmospheric river is a long, narrow band of water vapor that forms over an ocean and flows through the sky, transporting moisture from the tropics to northern latitudes.

Earlier this month, stubborn atmospheric rivers drenched Washington state with nearly 5 trillion gallons (19 trillion liters) of rain in a week, threatening record flood levels, meteorologists said. That rainfall was supercharged by warm weather and air, plus unusual weather conditions tracing back as far as a tropical cyclone in Indonesia.

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