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Flash flood threat in California prompts evacuation warnings from multi-day atmospheric river

If this storm unfolds as forecast, this would be one of Los Angeles' wettest Novembers in the past 50 years.

By Julian Atienza Source FOX Weather

California under flash flood threat, as atmospheric river set to bring several months' worth of rain

An atmospheric river will slam California beginning Thursday through early next week, delivering heavy rain, strong wind gusts and potentially feet of mountain snow. Flash Flood Warnings cover San Francisco and the Central Valley. The City of Los Angeles has issued evacuation warnings for areas around the burn scars from January's devastating wildfires. 

SAN FRANCISCO – An atmospheric river has begun to slam California that is expected to bring days of heavy rain, strong wind gusts and potentially feet of mountain snow to the Golden State through early next week, ushering in the region's rainy season.

The storm system is forecast to bring several months' worth of rain to Southern California in the span of just a few days, while a flash flood threat covers the Bay Area and Northern California Thursday.

WHAT IS AN ATMOSPHERIC RIVER?

Atmospheric river douses San Francisco morning commute with heavy rain

A powerful atmospheric river doused San Francisco morning commute with heavy rain Thursday morning.

Santa Clara County urged drivers to use caution Thursday morning. Meanwhile, while heavy rain fell during the height of the Thursday morning rush in San Francisco. 

A brief ground stop was issued at San Francisco International Airport due to high winds Thursday afternoon.

Meanwhile, the City of Los Angeles issued evacuation warnings around the Hurst and Sunset Fire burn scars from January's devastating wildfires through Sunday morning. Evacuation orders were also issued for areas around Mandeville Canyon which was within the footprint of the Palisades Fire.

WHAT IS A WILDFIRE BURN SCAR AND HOW COULD THEY HAVE LASTING IMPACTS?

Video Thursday morning showed Los Angeles firefighters going door-to-door in Pasadena warning people living in high-risk homes.

According to the National Weather Service, ash from wildfires creates burn scars – a water-repellent coating that prevents the ground from absorbing water and causes the area to be predisposed to flash flooding and debris flows.

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FILE - PACIFIC PALISADES,  CA  - OCTOBER 14, 2025 --  Workers clear debris from a business destroyed in the Palisades fire as scattered downpours, powerful winds and fears of flooding continue to threaten areas of the Pacific Palisades on October 14, 2025. The recent rain prompted evacuation warnings for residents near recent burn areas in the Pacific Palisades.  ((Genaro Molina/Los Angeles Times via Getty Images))

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FILE - PACIFIC PALISADES,  CA  - OCTOBER 14, 2025 --  Workers clear debris from a business destroyed in the Palisades fire as scattered downpours, powerful winds and fears of flooding continue to threaten areas of the Pacific Palisades on October 14, 2025. The recent rain prompted evacuation warnings for residents near recent burn areas in the Pacific Palisades. ((Genaro Molina/Los Angeles Times via Getty Images))

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FILE - LOS ANGELES, CALIFORNIA - OCTOBER 14: Water flows past trees in the Los Angeles River, swollen by storm runoff, on October 14, 2025 in Los Angeles, California. A strong atmospheric river storm is hitting Southern California today, triggering evacuation warnings in the Eaton and Palisades fire burn scars due to debris flow fears.  ((Photo by Mario Tama/Getty Images))

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FILE - CALIFORNIA, USA - FEBRUARY 6: A woman with an umbrella walks on a road during heavy rain in Guerneville of Sonoma County, California, United States on February 6, 2025 as an atmospheric river hits Northern California.  ((Photo by Tayfun Coskun/Anadolu via Getty Images))

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FILE - LOS ANGELES, CALIFORNIA - FEBRUARY, 5: An abandoned car sits in floodwaters during an atmospheric river storm in Los Angeles, California on Monday, February 5, 2024. (Photo by Kyle Grillot for The Washington Post via Getty Images) ( )

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FILE - A car drives through a flooded street in Rosemead, California, on Oct. 14, 2025.  (Photo by Frederic J. Brown / AFP) (Photo by FREDERIC J. BROWN/AFP via Getty Images)

According to the FOX Forecast Center, rain is expected to sweep across coastal California and farther inland in the Central Valley Thursday.

NOAA's Weather Prediction Center issued two different Level 2 out of 4 flash flood threats Thursday, one that covers San Francisco and the Bay Area, the other covers Sacramento and parts of the Shasta Cascades, Sierra Nevadas and Gold Country.

Thunderstorms with lightning and strong wind gusts are possible as storms come onshore. 

KNOW YOUR FLOOD TERMINOLOGY: WHAT FLOOD WATCHES, WARNINGS AND EMERGENCIES REALLY MEAN

The more intense rain and the flood threat will move into Southern California Thursday night through the Friday morning commute. A second round is forecast to begin Friday evening.

All told, parts of the California coast, including San Francisco and Los Angeles, could see 3-5 inches of rain through Monday, with localized pockets of 5-8 inches of rain. The San Gabriel and Santa Monica ranges could also see 5-8 inches of rainfall.

A NEW TECH APPROACH TO FIGHTING WILDFIRES

If this storm unfolds as forecast, this would be one of Los Angeles' wettest Novembers in the past 50 years.

DRIVING ON THE ICE AND DRIVING IN THE SNOW

Meanwhile, winter weather alerts have been posted for the Sierras through Friday. Some of the highest mountain passes have already closed for the season.

Wind gusts along ridgetops in the Sierras could exceed 100 mph.