An atmospheric river storm pumped drenching rains into the heart of California on Thursday as blizzard conditions buried the Sierra Nevada in snow.

The storm was aimed like a massive firehose at the central coast, where two-day rainfall before dawn exceeded 12 inches (30.48 centimeters) in San Luis Obispo County, the National Weather Service said. 

In the Eastern Sierra, the Mammoth Mountain ski resort reported 6.3 feet (1.93 meters) of new snow on its summit.

Wide areas of the state remained under warnings and watches for flooding, heavy snow and winds. The storm was expected to begin moving after its overnight stall and drop down into Southern California, bringing threats of debris flows, mudslides and flash floods to areas near huge wildfire burn scars.

Three years ago, a Jan. 9, 2018, downpour unleashed a debris flow from a massive wildfire burn scar — smashing through the Santa Barbara County community of Montecito and killing 23 people. 

This storm’s peak rainfall rates in the region could reach up to 0.75 inches (1.9 centimeters) an hour, with up to 3 feet (0.91 meter) of snow in the mountains, the National Weather Service said.

The storm punched into Northern California late Tuesday night and continued on Wednesday, drifting down the coast and stalling over Big Sur before pivoting back northward. 

Mudslides near Salinas south of the Bay Area damaged about two dozen rural ranch homes beneath hillsides scorched by the River Fire last August, said Dorothy Priolo with the Monterey County Regional Fire Protection District. 

One woman was treated for broken bones after mud went “completely through the house” in the early morning hours, Priolo said. Fifty horses were rescued.

The threat of flooding from fire-scarred areas persisted overnight in the Santa Cruz mountains, where about 5,000 people remained under evacuation orders.

Parts of the San Francisco Bay Area could have thunder, lightning and even hail into Thursday afternoon, according to the weather service.

Flash flood warnings remained in effect through Thursday afternoon for parts of Santa Cruz and San Mateo counties, Monterey County and areas of the northern San Francisco Bay Area, especially those near burn areas.

In the city of Paso Robles, authorities urged homeless people camped in the bed of the Salinas River to head for higher ground because the river could rise as much as 25 feet (7.6 meters). Some had left but others moved their tents higher and hoped for the best, KSBY-TV reported.

State and local teams with specialized rescue skills were positioned in five counties because of flooding threats.

The storm topped trees and knocked down power lines through a wide swath of the north. Pacific Gas & Electric said about 575,000 customers lost power Tuesday and Wednesday. 

One gust hit 125 mph (201 kph) at Alpine Meadows near Lake Tahoe. 

A blizzard warning was in effect through Friday morning on both sides of the California-Nevada border along a 170-mile (274-kilometer) stretch of the Sierra.

“This is a life-threatening situation. Do not attempt to travel,” a weather service warning said. “Road crews and first responders may not be able to rescue you. Stay indoors until the snow and wind subside. Even a short walk could be deadly if you become disoriented.”

Schools closed in several Nevada counties.

The atmospheric river is part of a major change in weather for California, which had significant drought conditions for months. The dryness contributed to wildfires that scorched more than 4.2 million acres (17,000 square kilometers) in 2020, the most in recorded modern history.


Antczak reported from Los Angeles. Associated Press writers Christopher Weber in LA and Scott Sonner in Reno, Nevada, contributed to this report.