Extreme Weather in California Causes Flooding and Landslides

Heavy rain and snow caused landslides and flooding in Northern California on Saturday, shutting down two major highways as another “atmospheric river” system pounded the West Coast.

The rain is expected to let up in Northern California by Saturday evening, but some rivers and streams are already reaching flood stage levels. Mud and rockslides have occurred in some parts.

An hourslong torrent of rain forced Highway 101 to close south of San Francisco because of flooding, cutting off a major route between the city and the Silicon Valley. Flooding also has forced the closure of Highway 50 in the Sierra Nevada, potentially stopping New Year’s revelers and skiers from reaching South Lake Tahoe for the holiday weekend.

The Cosumnes River in Northern California exceeded flood stage and was expected to crest at 15.5 feet by Saturday night. Parts of the state have already had up to seven inches of rain from Friday to Saturday.

In Southern California, light to moderate rain will fall in the Los Angeles area on Saturday accompanied by strong wind gusts through the evening, forecasters said. A high-wind warning is in place for most of the area’s mountains and the Antelope Valley.

While the intense storm has made for a chaotic Saturday morning on the roads, it has brought relief to a state enduring another prolonged drought.

An atmospheric river, a weather pattern that causes extreme rainfall and winds, will renew the potential for flooding in Northern California Wednesday into Thursday, forecasters said.

An unusually strong and long-lasting atmospheric river on the West Coast just after Christmas led to the deaths of five people after trees fell on vehicles in three separate episodes, the authorities in Oregon said. Tens of thousands in the Pacific Northwest lost power.

Significant flooding is expected in the Sacramento area until 10 p.m. on Saturday, and heavy snow at higher altitudes, National Weather Service forecasters said. The Bay Area is under a flood advisory until 11:45 a.m. local time, and wind advisories for the area remain in effect throughout the day.

Drivers who find roads that are flooded are encouraged to turn around, officials said. Sacramento firefighters rescued several teenagers from tree limbs early on Saturday after their car was immobilized by flooding. No injuries were reported, the authorities said.

Up to two inches of rain are expected south of the area around Chico, another two to three inches to the east of the valley and three to five inches along the northern Sierra western slopes.

“Significant runoff from this rain is expected to quickly lead to more widespread stream and nuisance urban flooding this morning,” forecasters said. “Mainstem rivers and tributaries will see rises associated with runoff and/or dam releases.”

Highway 92 from Skyline Boulevard to Main Street in Half Moon Bay was closed because of flooding. A part of Alameda State Road 84 in the Bay Area was reopened Friday after having been closed for several hours as workers cleared a landslide.

The greatest risk of the extreme weather earlier this week was in previously burned areas along the coast, William Churchill, a forecaster and meteorologist with the National Weather Service’s Weather Prediction Center in College Park, Md., said this week. Rapid, prolonged rainfall could cause mudslides or debris flows, he said.