SACRAMENTO — A powerful winter storm system was moving across California on Thursday, toppling trees, knocking out power and bringing more rain, wind and snow to the already battered state.
The storm, one of several that is expected to pound the West Coast this month, moved on shore from the Pacific Ocean overnight, whipping across San Francisco with heavy rain and high winds and bringing heavy snow in the Sierra Nevada.
Forecasters cautioned that a combination of high winds and saturated ground conditions could topple trees, leading to power outages. As of Thursday morning, about 170,000 customers were without electricity in the state, according to the tracking site poweroutage.us.
High winds toppled a tree onto power lines near a set of train tracks, shutting down rail service Thursday morning in Burlingame, near San Francisco International Airport. And a mudslide was blocking one lane of Highway 1, according to the police in Pacifica, which is also south of San Francisco.
Bay Area Rapid Transit, which ferries thousands of commuters to work each day, warned of systemwide delays on Thursday because of downed trees and continuing wet weather conditions.
As the sun rose in San Francisco, crews were working to remove trees and clean streets littered with debris from the heavy winds. Near the city’s main public library, a family was rescued after a tree fell onto their car on Wednesday night. “Falling trees continue to be a concern,” the library warned on Twitter after the incident.
The authorities blamed at least two deaths on Wednesday on the storm. In Fairfield, Calif., northeast of San Francisco, a 19-year-old woman died after the car she was driving hydroplaned and crashed into a utility pole, the police said. And a 2-year-old was killed when a redwood tree fell on a mobile home in Occidental, a rural community in Sonoma County, said Josh Cerda, a firefighter engineer with the local volunteer fire department.
Up to three inches of rain fell overnight around Northern California and about an inch and a half in Sacramento, Johnnie Powell, a meteorologist with the Weather Service in Sacramento, said Thursday morning. Winds peaked at around 60 miles per hour in Redding and at about 50 m.p.h. in the Sacramento region, he said.
Parts of Southern California’s coast could see heavy rains later on Thursday. That moisture raised the prospect of rapid runoff along the state’s coast and interior valleys, as well as in the Sierra Nevada foothills and in areas around burn scars left by wildfires, a Weather Service advisory said.
As a result, several school districts around the Bay Area canceled classes on Thursday. Over a dozen school districts in flood-prone San Mateo County, just south of San Francisco, announced they would be closed on Thursday, as did nine in Sonoma County.
Some parks across Northern California were also either partially or fully closed for the day.
The storm is part of a series of atmospheric rivers — channels of moisture from the tropical Pacific Ocean. Further rounds of heavy precipitation are expected to hit California on Saturday and again on Monday.
Scientists are not sure how climate change affects the likelihood that atmospheric rivers will crash into California’s coast in rapid-fire succession again. Scientists are studying whether global warming might be shifting the way winds carry moisture around the atmosphere.
When such storms are particularly severe or sweep through in rapid succession, they can deliver too much water too quickly to a state that has lately been parched by drought and scorched by wildfires.
“This is an extreme weather event, and we’re moving from extreme drought to extreme flood,” Karla Nemeth, the director of California’s Department of Water Resources, told reporters on Wednesday. “What that means is a lot of our trees are stressed. After three years of intensive drought, the ground is saturated and there is significant chance of downed trees that will create significant problems.”
California has taken a pounding this month, even as the heavy rain and snow have brought a measure of relief to the state’s giant agricultural industry. An atmospheric river that drenched the West Coast last week killed at least five people in Oregon. A related storm hit earlier this week, causing widespread flooding in the Bay Area and at least four deaths in California.
In Elk Grove, south of Sacramento, the Wilton Rancheria tribe said on Tuesday that flooding had damaged sacred burial grounds along the Cosumnes River in Wilton, imperiling “hundreds of unmarked Wilton Rancheria ancestral burial sites.”
With more bad weather on the way, Gov. Gavin Newsom declared a state of emergency on Wednesday, saying that he expected more highway closures, infrastructure failures and mandatory evacuations in the coming days.
Several communities across California issued evacuation orders, including in an area of San Benito County, south of San Jose, where a failure at a hydropower dam was expected to produce flooding.
Christine Hauser, Soumya Karlamangla, Victoria Kim and Derrick Bryson Taylor contributed reporting.
