LOS ANGELES — A storm fueled by a plume of moisture stretching over the Pacific Ocean almost to Hawaii dumped rain on California Thursday, boosting the threat of debris flows from saturated slopes and flooding from rising creeks and rivers.
The storm made stronger by the phenomenon called an atmospheric river hit Northern California and southern Oregon on Wednesday before moving down the coast overnight and threatening the southwestern corner of California.
Flash flood warnings were issued for residents living near slopes burned bare by a summer wildfire in the Santa Ana Mountains southeast of Los Angeles.
Earlier, a woman was rescued from the wreckage of her Northern California home after it slid down a hill. KNTV reported at least 50 homes were evacuated after the mudslide struck a neighborhood in Sausalito, north of San Francisco.
Atmospheric rivers are long bands of water vapor that form over an ocean and flow through the sky. Formed by winds associated with storms, they occur globally but are especially significant on the West Coast. When an atmospheric river originates near Hawaii it is commonly referred to as a “Pineapple Express.”
South of San Francisco, authorities urged people to leave homes near the Guadalupe River in San Jose. Forecasters also said numerous other rivers were expected to crest over flood stage on Thursday.
The tempest followed more than a week of severe weather in the Pacific Northwest and was the latest in a series that has all but eliminated drought-level dryness in California this winter.
Even before the height of the storm, mandatory evacuations were ordered near the burn scar in the Santa Ana Mountains where officials said the risk of debris flows was high.
Tim Suber said he has lost count of how many times his hillside neighborhood in Lake Elsinore has been evacuated between last summer’s devastating wildfire and this winter’s succession of storms.
“I’m not going this time,” Suber said Wednesday after Riverside County sheriff’s deputies warned him that he could end up trapped if roads flood. “I’ve got 35 chickens and a daughter who won’t leave them behind. So we’re staying.”
The real estate agent said he was confident culverts and washes in the area will handle any runoff after crews removed dozens of truckloads of dirt following the last storm. But just in case, “my car is gassed up and ready to go at a moment’s notice,” said Suber, 54.
Winter storm warnings were posted in the snow-laden Sierra Nevada, where the forecast said up to 7 feet (2.1 meters) of new snow could be dumped at elevations above 9,000 feet (2,743 meters).
The National Weather Service recorded winds gusting to 132 mph (213 kph) atop the Mount Rose ski resort southwest of Reno, Nevada.
A backcountry avalanche warning was issued throughout the Sierra.
Five passengers suffered minor injuries when a Delta Air Lines flight headed from Southern California to Seattle encountered severe turbulence in the storm and was forced to make an emergency landing in Reno. Photos on social media showed a drinks cart upended and snacks and soda cans littering the aisle. One passenger tweeted the plane did two nose dives in “crazy turbulence” but the crew “handled it perfectly.”
On Wednesday, snow heavily impacted stretches of vital Interstate 5 in far Northern California, causing closures and forcing tire-chain requirements.
A local state of emergency was declared in Shasta County because of significant storm damage, a Sheriff’s Office statement said. Redding, the county seat, turned its library into a warming center.
Power outages also hit thousands of utility customers in the region.
Widespread roadway flooding occurred north of San Francisco Bay. To the east, a swath of California’s Central Valley was under a flood warning.
At one point, flight arrivals at San Francisco International Airport were experiencing delays of several hours, the Federal Aviation Administration said.
In Washington, thousands of Puget Sound Energy customers lost power, and Interstate 90 was closed for a second day Wednesday across Snoqualmie Pass in the Cascade Mountains. The town of North Bend declared a state of emergency because of several feet of snow.
In Oregon, transportation officials closed about 20 miles of the westbound lanes of Interstate 84 in the Columbia River Gorge east of Portland because of icy conditions that caused numerous wrecks and stranded drivers for hours.
Authorities brought stranded travelers water and food and tried to get gas to vehicles that needed it.
The West’s winter storms have greatly aided California’s water supply.
The most recent Sierra snowpack survey taken on Jan. 31 was 100 percent of normal to date. More snow has fallen since.
In the Eastern Sierra, the Mammoth Mountain resort reported the latest storm had already added 8 inches (20.3 centimeters) to its summit season total, which is nearing 38 feet (11.5 meters).
Mammoth said it planned to keep its slopes open to skiing and boarding through the Fourth of July, at least.
