The first of two “pineapple express” storms has arrived in Southern California after delivering a stronger-than-expected pounding to the San Francisco Bay Area, breaking rainfall records.
A house in the Sonoma County town of Forestville fell into the Russian River after a rain-saturated hillside gave way, and all low-lying areas of the river downstream of Healdsburg — including Guerneville — were ordered evacuated due to the risk of flooding. Roadways flooded across the region, including lanes on U.S. 101 in Windsor, near Santa Rosa, as well as Interstate 5 and California 99 in San Joaquin County. A large tree branch in San Francisco’s Visitacion Valley fell and hit a person, who declined to be taken to a hospital.
About 15,000 customers were affected by power outages early Wednesday morning, according to Pacific Gas & Electric Co.
The storm is expected to be weaker in Southern California.
Meteorologists say Wednesday’s gusty atmospheric river storm is capable of causing roads to flood and triggering rockslides on canyon roads. But it will probably be generally beneficial for Los Angeles and Ventura counties, helping to reduce the risk of wildfires.
The National Weather Service estimates there’s a 5% to 10% chance of significant debris flow in fire-scorched parts of the two counties, as well as in the burn area of the 2024 Lake fire in the Santa Barbara County mountains north of Los Olivos.
Gusts from the south and southwest, at 15 to 30 mph, will be common in L.A. and Ventura counties — and up to 50 mph in the high desert. They are expected to peak from 10 p.m. Tuesday through 10 a.m. Wednesday, possibly causing delays at Los Angeles International Airport and isolated power outages, meteorologist Kristan Lund of the weather service’s Oxnard office said. Gusts could be even stronger in Santa Barbara and San Luis Obispo counties, causing trees to fall.
Northwestern San Luis Obispo County is an area of concern. Through Wednesday morning, 4 to 8 inches of rain could fall in the Santa Lucia Range, the mountains that tower over coastal towns including Morro Bay, Cambria and San Simeon as well as the Big Sur area.
“That is a lot of rain in that time period. So we are a little bit concerned about increased creek flows” and impacts to California 1 in northwestern San Luis Obispo County, Lund said.
Officials are preparing for potential landslides and mudflows in Southern California. An 8½-mile stretch of Pacific Coast Highway was shut starting Tuesday afternoon — between Chautauqua Boulevard in Pacific Palisades and Carbon Beach Terrace in Malibu — because of the risk of debris flow. A four-mile stretch of Topanga Canyon Boulevard, ending at the Pacific Ocean, was also closed.
The first atmospheric river storm in Southern California was expected to begin tapering off after about 10 a.m. Wednesday in Los Angeles and Ventura counties. The second is forecast to be weaker, and expected to peak Thursday afternoon and evening. There will still be chances of rain between the two storms and through early Saturday morning.
From Friday night through Monday, there’s a potential for dry winds gusting into the region — from 15 mph to as high as 50 mph in wind-prone areas — but the risk of fire weather is minimal, given the recent rains, Lund said. Relative humidity could fall to 12% in Santa Clarita, 13% in Canoga Park and 17% in Thousand Oaks. Areas including downtown L.A., Covina and Long Beach will see higher relative humidity, at around 30%, and Redondo Beach, 43%.
It’s a Santa Ana-style wind event, which brings gusty winds and relatively dry air into the region. Since the winds are generally coming out of the north, it’s not considered a “pure” Santa Ana, when winds come out of the northeast, said meteorologist Ryan Kittell of the weather service’s Oxnard office.
“These winds will not affect all the same areas as a true Santa Ana would,” Kittell said, “and it will not be as dry as one would expect.”
Even with this week’s rains, the amount of precipitation that has fallen will probably not be enough to declare an end to fire season, given the region’s severe deficit in winter rainfall.
The week’s rainfall totals are expected to be modest — for downtown Los Angeles, 0.43 of an inch for the first storm and 0.41 for the second. Combined with the 0.54 of an inch downtown received from Jan. 25-27, that’s less than 1½ inches. Meteorologists say 2 to 4 inches of widespread rain are necessary to definitively call an end to the fire season.
“While the rains will have provided temporary relief with high moisture in some fuel types, the expected rain this week will not be enough to completely end high fire season,” Lund said.
“If we got a really dry Santa Ana next week, instead of a rainstorm, we could still have [the] potential for extreme fire behavior,” the meteorologist said. Given Southern California’s severe precipitation deficit, she said, a lack of rain for a week or two combined with the arrival of dry, strong winds from the high desert could mark a return to fire weather danger.
Forecasters, however, are monitoring the potential for another storm that could arrive in the middle of next week, between Feb. 12 and Feb. 15. There’s a 10% chance of high amounts of rain, a 40% chance of moderate amounts and a 30% chance of low amounts. The chance of no rain is 20%.
For this week’s first storm, Santa Clarita could get 1/7 of an inch of rain; Covina, 3/10 of an inch; downtown Los Angeles, Canoga Park and Long Beach, 2/5 of an inch; Redondo Beach, about half an inch; Thousand Oaks, 3/5 of an inch; Oxnard, 2/3 of an inch; San Luis Obispo, 1.16 inches; and Santa Barbara, 1.69 inches.
For the second atmospheric river storm, downtown Los Angeles, Canoga Park, Redondo Beach, Long Beach, Santa Clarita and Thousand Oaks could get 2/5 of an inch of rain; Covina and Oxnard, about half an inch; and Santa Barbara and San Luis Obispo, about 3/5 of an inch.
For San Diego and Orange counties and the Inland Empire, the storm will be even weaker, and there may be occasional periods of rainfall through Friday night.
For the two storms combined this week, San Diego could get up to 1/5 of an inch of rain; Riverside, up to 3/10 of an inch; San Bernardino and Oceanside, up to 2/5 of an inch; Irvine and San Clemente, up to half an inch; and Anaheim, up to 7/10 of an inch.
Across Northern California, Tuesday’s atmospheric river — the second for that region since Friday — packed a punch. A gust of wind hit 90 mph in the mountains of Marin County, another was clocked at 69 mph at San Francisco International Airport, and one gust hit 55 mph in San Francisco.
Downtown San Francisco got 2.89 inches of rain Tuesday, breaking the record for the calendar day last seen in 1887, when 2.22 inches of rain was observed. San Francisco International Airport recorded 1.75 inches, breaking the record of 1.3 inches on Feb. 4, 1991.
And the Charles M. Schulz-Sonoma County Airport near Santa Rosa recorded 2.72 inches, breaking the record for the calendar day set last year, when 1.85 inches fell.
Since Friday, more than 17 inches of rain have been recorded at Mt. Tamalpais in Marin County.
On Tuesday, there were reports of landslides across the North Bay, with urban and stream flooding. Flooding closed several roads in Marin County, including California 1 between Point Reyes Station and Bear Valley Road.
The Russian River in Guerneville was forecast to reach minor-flood stage early Wednesday. That level of flooding could begin to flood the lowest sections of towns along the river, according to Sonoma County.
Mud from a hillside flowed into an apartment building in the town of Fairfax in Marin County, according to KPIX-TV. No injuries were reported.
In San Francisco, a pothole measuring about 5 feet by 4 feet opened up in the Marina District amid heavy rain. A KGO-TV news crew reported that multiple autonomous Waymo cars drove through the pothole at full speed, ignoring efforts by crews to get the vehicles to avoid the hazard.
Trees also fell in the East Bay and San Mateo County, TV stations reported.
On Tuesday afternoon, a severe thunderstorm warning was issued for San Francisco and swaths of San Mateo and Marin counties, bringing warnings of gusts of up to 70 mph and the potential for considerable damage to trees, roofs and mobile homes.
Evacuations were ordered at a medical facility in Santa Rosa and a neighboring Hampton Inn after parking lots flooded, partially submerging some cars, the Press Democrat reported.
Flooding temporarily forced the closure of some southbound lanes of Interstate 5 in Stockton. Farther north in San Joaquin County, southbound California 99 had to be shut in Lodi due to the flooding Tuesday night.
In Mendocino County, significant flooding was expected along California 175 at the Russian River near Hopland, and moderate flooding was expected at the Navarro River at Navarro, the weather service office in Eureka said.
Moderate flooding was also forecast for the Susan River in Susanville in Lassen County, the weather service office in Reno said.
In the Sierra, officials issued a backcountry avalanche warning for the Lake Tahoe area Tuesday because of heavy snow, rain falling on snow and strong winds. The warning is expected to last through Wednesday.
In the Greater Lake Tahoe area, forecasters expected 1 to 3 feet of snow at elevations 7,000 feet above sea level and higher, and 6 to 12 inches below that elevation.
In Mono County, which includes Mammoth Mountain, 1 to 3 feet of snow was expected to accumulate at elevations above 8,000 feet, and up to 6 inches below that elevation.
Snow levels in L.A. County will remain above the 6,500-to-8,000 feet elevation.
The wet weather comes after a disastrous start to 2025 for Los Angeles County, with the Eaton fire scorching more than 14,000 acres in the Altadena area and the Palisades fire burning 23,400 acres on the Westside of Los Angeles. More than 16,000 structures, including many homes, were destroyed in the firestorms, and 29 deaths have been recorded.