California declares state of emergency over powerful winter storm

California Governor Gavin Newsom has proclaimed a state of emergency throughout the most populous state in the US, to support the ongoing response to a powerful winter storm.

"California is mobilising to keep people safe from the impacts of the incoming storm," and the state of emergency will allow the state to respond quickly as the storm develops and support local officials in their ongoing response, Newsom was quoted by Xinhua news as saying.

The governor on Wednesday noted in his proclamation that severe winter storms related to a series of atmospheric river systems has struck California, home to around 40 million residents, since last week. It is forecast that additional and continuing related storms threaten California, bringing heavy rainfall, expected flooding, strong winds and wind gusts, falling debris, downed trees, and widespread power outages.

The emergency proclamation supports emergency relief efforts including authorising the mobilisation of the California National Guard to support disaster response.

A powerful hurricane force low pressure system located over the eastern Pacific is set to surge a plume of moisture and damaging winds into the US West Coast beginning Wednesday night. The greatest impacts, which include damaging winds, excessive rainfall, and extremely heavy snow, is forecast to occur over much of California and into southern Oregon through Thursday, according to the US National Weather Service.

Recent burn scars and other sensitive terrain will have the greatest chances for rapid runoff and mudslides as rain rates potentially exceed 1 inch per hour, the agency said, adding that flood and flash flood watches, high winds warnings, and winter storm warnings are in effect from southern Oregon to southern California.

The California Governor's Office of Emergency Services said it has strategically prepositioned critical resources near burn scar areas in seven counties in the state -- Los Angeles, Orange, Contra Costa, Lake, Monterey, Sonoma and El Dorado -- as well as five other counties with major flooding concerns.

"The public is urged to be on the lookout for potential flooding and mudslides in areas recently burned by wildfires. A debris flow can take homes off their foundations and carry items such as vegetation, large boulders, and cars," said the agency in a news release.

"If you live near or downslope of burn areas, you should have a plan to quickly evacuate your community if flash flooding or a mudslide were to happen," the agency added.

"We anticipate that this may be one of the most challenging and impactful series of storms to touch down in California in the last five years," Nancy Ward, director of the Governor's Office of Emergency Services, was quoted as saying by the Los Angeles Times, the biggest newspaper on the US West Coast.

The California Department of Transportation urged the public in the state to limit nonessential travel due to the severe winter storm.

"Try to limit your time on the roads during the peak of the storm on Wednesday night," the agency said on social media.