Updated

The Latest on storms in California (all times local):

12:05 p.m.

Officials say about 21,000 people have been evacuated from neighborhoods beneath hillsides laid bare by California's largest-ever wildfire and other recent blazes as a storm raises fears of flash floods and debris flows.

Robert Lewin, director of the Santa Barbara County Office of Emergency Management, is urging residents of Summerland, Carpinteria and Montecito to leave by mid-Monday. The hillside communities were evacuated last month as the massive Thomas Fire raged. Evacuations also include homes near other burn areas dating to 2016.

Lewin says flash floods can turn normally dry creeks into destructive rivers of mud and debris that can wash out roads and destroy homes.

The first significant storm of the season is walloping much of the state with heavy rain, snow and strong winds. Forecasters say several inches of rain could fall overnight on areas scarred by the largest-ever state blaze.

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11:45 a.m.

Thousands of sandbags are being made available to the public in Southern California areas susceptible to flash floods and debris flows as the first significant storm of the season moves into the region.

In Ventura County, where the huge Thomas Fire began in December, the Sheriff's Office says jail inmates have been filling sandbags at the rate of 2,000 a day.

The county has also acquired 40,000 surplus sandbags from the U.S. Defense Department and purchased others to distribute to the public at fire stations.

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8:30 a.m.

A flash flood watch has been issued for parts for Northern California and forecasters are warning rainfall the next two days could trigger mudslides in areas devastated by wildfires in October.

A storm moved in to the San Francisco Bay Area early Monday, snarling traffic during the morning commute and causing several accidents. No major injuries have been reported.

The flash flood watch is in effect from noon Monday to 6 a.m. Tuesday and officials in Santa Rosa, one of the areas hardest hit by last year's wildfires, say crews are standing by in case they are needed.

The National Weather Service has also issued a winter weather advisory for portions of the Sierra Nevada because higher than usual snow levels are expected Tuesday. The advisory says travelers should be wary of slippery roads, gusty winds and low visibility.

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This story has been corrected to show a flash flood watch not a warning has been issued.

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5:25 a.m.

Evacuations have been ordered for communities below hillsides charred by California's largest-ever wildfire as the first major winter storm of the season brings rare rain and raises the risk of mudslides.

The wet and windy system moving ashore Monday could soak much of the state and drop several inches in parts of Santa Barbara and Ventura counties, where the Thomas fire has burned for more than a month and left hillsides bare.

Residents of Montecito, Summerland and Carpinteria who were evacuated because of flames in December were ordered to leave again because rains could wash dirt and debris down into neighborhoods.

About an inch of rain is forecast for downtown Los Angeles, the most in nearly a year.

Snow could make for treacherous driving conditions in mountain areas early Tuesday.