A massive winter storm bearing down on California threatens snow by the foot across some of its highest mountains, along with the potential for flooding, tornadoes and damaging winds south to Los Angeles through the middle of the week.

Wind, snow and flood watches, warnings and advisories stretch across the state’s length, the National Weather Service said. The rain was expected to intensify starting Sunday evening and last through Wednesday.

In a post on X, the California Governor’s Office of Emergency Services urged residents “to be prepared for cascading impacts of severe weather and storms, including floods, landslides, power failures, and road closures.”

High winds, heavy rain and snow may lead to widespread power outages, as well as disruptions to air travel through the region.

Los Angeles Mayor Karen Bass ordered an evacuation warning for neighborhoods in the burn scar of last year’s wildfires, including Palisades, Sunset and Hurst, because of the risk of landslides. The warning is scheduled to last from 9 p.m. Sunday to 9 a.m. Tuesday.

“This is likely to be another significant rain event. All Angelenos – especially those in burn scar areas – are encouraged to follow official guidance, use caution on the roads, plan ahead, and stay informed,” Bass wrote on X.

The National Weather Service earlier Sunday issued backcountry avalanche warnings for the Eastern Sierra in Mono County, which includes Mammoth Lakes, and the greater Tahoe region. Separately, the Governor’s Office of Emergency Services has “prepositioned fire and rescue personnel” in areas at risk for flooding, and debris flows, according to a statement.

California has some of the most volatile weather in the U.S. — especially in winter, when conditions can be calm for weeks only to give way to large storms rolling in off the Pacific.

The most populous U.S. state saw a series of such systems earlier in the season, though most have come during warmer weather, leaving California and much of the West without the deep snow pack needed to ensure water supplies will be plentiful through the rest of the year.

The latest storm may help by building up a frozen reservoir in the mountains that can be tapped later in the year when the dry season starts.

The storm will begin to uncoil late Sunday, with colder temperatures and a lot more snow. Winter storm warnings have been posted in the mountains just north of Los Angeles, where up to 12 inches or more of snow is forecast above 4,500 feet along with winds gusting to 70 miles per hour, said Ashton Robinson Cook, a forecaster at the U.S. Weather Prediction Center.

“There is a fairly strong system out in the West that is slowly approaching California,” Robinson Cook said. “There is a lot of complex terrain, so there is a lot of weather variation in a short amount of space.”

Southern California is in line for heavy rain, with up to 4 inches expected to fall along the coast and valleys and as much as 8 inches in some mountains and foothills, the weather service said. Flood watches have been posted throughout the region, warning that rock and mud slides are likely as well as debris flows in areas scarred by recent wildfires.

Thunderstorms and heavy rain could bring urban flooding to San Francisco, Robinson Cook said. In addition, tides throughout the Bay Area may be 12 to 18 inches higher than normal, causing some coastal flooding.

As much as 8 feet of snow is forecast in many areas of the Sierra Nevada range above 3,500 feet. This will cause headaches for residents and travelers looking to drive across mountain passes. “This is a long duration event for some of the higher terrain,” Robinson Cook said.

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(With assistance from Alicia A. Caldwell.)

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