A large swath of California was bracing on Thursday for an intense bout of rain that could lead to flooding and cause debris flows in areas recently burned by wildfires.
The Southern California regions scorched by flames last month were of particular concern because the soil in those areas can repel water and allow sheets of water to race downhill and collect debris along the way.
In the Los Angeles area, about two inches of rain was expected over the next two days, but some parts of Southern California could receive more than four inches, according to the National Weather Service. A torrent of rain within a short period could pose particular problems.
As light to moderate rain fell across Southern California on Thursday morning, officials warned that the storm would intensify later and pose problems. If heavy rain falls over the burn scars, “there will be the potential for very severe debris flows to occur in addition to mudslides and rock slides,” said Ariel Cohen, the meteorologist in charge of the National Weather Service office that oversees the Los Angeles region.
“Everyone needs to be at a high state of readiness,” Dr. Cohen added.
More than 100 homes were under mandatory evacuation orders in the city of Los Angeles, said Jim McDonnell, the Los Angeles Police Department chief, on Thursday morning. The Palisades fire destroyed thousands of homes in the city’s Pacific Palisades neighborhood last month, and hillsides remain vulnerable in the area.
Elsewhere in Los Angeles County, evacuation warnings and orders were issued for areas recently affected by the Eaton fire, which burned more than 14,000 acres and destroyed more than 9,400 structures. On Thursday morning, some residents in Sierra Madre, Calif., were told to evacuate before the worst of the storm.
Sheriff Robert Luna of Los Angeles County said at a news conference on Wednesday that officials had been notifying residents in areas with elevated risk, and he urged residents to heed to any evacuation orders they received.
“Storms can bring sudden and severe conditions that make staying back home extremely risky,” Sheriff Luna said. “Do not take that chance.”
Landslides could prevent law enforcement personnel and emergency crews from being able to reach those in need, Sheriff Luna added.
Concerns this week extended beyond areas affected by the Palisades and Eaton fires. Mark Pestrella, the director of the Los Angeles County Public Works Department, said on Wednesday that any burn scar area from a fire within the past year could be at risk. In Orange County, the Sheriff’s Department issued an evacuation warning for the area near the site of the Airport fire, which burned more than 20,000 acres in the foothills of the Santa Ana Mountains. In Malibu, all public schools were closed on Thursday because of the storm.
The California Governor’s Office of Emergency Services said that, to prepare for the heavy rain, it had positioned resources across 14 counties, from Sonoma County in Northern California to San Diego County at the southern border.
Intense storms were also being forecast for Thursday in the Bay Area and other parts of Northern California, but they were not expected to cause as many problems as in Southern California. On Thursday morning, the Santa Cruz County Sheriff’s Office issued an evacuation order for parts of the county because of rising creek levels.
Officials in Santa Barbara County, which experienced a deadly mudslide in 2018 along with flooding in recent years, have been preparing for the storm since late last week, said Jackie Ruiz, a spokeswoman for the county’s emergency management office.
“We had back-to-back years of pretty intense rain here,” Ms. Ruiz said, “so it’s something that we’re very familiar with in the community.”
On Wednesday, sheriff’s deputies were knocking on the doors of about 50 properties within the burn scar area of the Lake fire, which burned more than 38,000 acres last year, Ms. Ruiz said. Officials were also trying to reach people who live in encampments in creek beds, underpasses and other places that are prone to flooding, she said.
In San Luis Obispo County on the Central Coast, officials were preparing for possible flooding as severe as what occurred in January 2023, when heavy rainfall inundated communities. During that storm, a 5-year-old boy was swept away and killed when floodwaters overwhelmed his mother’s vehicle. A flood advisory was in effect in the county on Thursday.
Jonathan Wolfe and Amanda Holpuch contributed reporting.
