A powerful storm was hitting Southern California Thursday.
The second of two atmospheric-river-fueled storms to hit Southern California this week is moving faster than originally anticipated but is still bloated with moisture. It’s expected to dump 1 to 2 inches of rain along the coast and up to 4 inches in the valleys at rates that could cause problems.
“Fire-impacted communities need to be on alert,” Los Angeles County Supervisor Kathryn Barger said during a news conference Wednesday morning. “The risk of mudflow and landslides is real. Play it safe and be prepared.”
The National Weather Service plans to issue a flood watch beginning at 6 p.m. Wednesday and lasting through Thursday afternoon, warning of the possibility of flash flooding and debris flows caused by excessive rainfall. The alert will cover much of Los Angeles and Ventura counties, and the south coast of Santa Barbara County.
The heaviest rain is expected to fall through early Thursday in Los Angeles County.
There is a possibility of heavier showers and thunderstorms hitting the southwest-facing mountains and foothills, areas that are prone to such storm patterns. Damaging winds, heavy downpours, hail and even a weak tornado are possible, said Rose Schoenfeld, a meteorologist with the National Weather Service in Oxnard.
“The most likely outcome is that we’re going to see shallow to minor debris flows, minor flooding and some amount of ponding and flooding on roadways,” Schoenfeld said.
However, she added, there’s also a 30% to 50% chance of significant flooding and debris flows for areas in the flood watch, particularly the burn scars. Officials have said there’s a high chance of rainfall rates exceeding 0.75 of an inch per hour, which could trigger significant debris flows in fire-scarred areas.
“This could include impacts such as roads being covered by mud or water, cars stuck in mud or water, and some amount of structures threatened in burn scars,” Schoenfeld said.
Evacuation warnings and orders have been issued for Los Angeles communities near the Eaton, Palisades and Sunset fire burn zones ahead of the rain.
In the Palisades burn scar, the Getty Villa area, the Highlands, the Bienveneda area near Temescal Canyon Park, Rivas Canyon/Will Rogers State Park, Mandeville Canyon above Tanners Road, Old Ranch Road and Rustic Creek are under evacuation warnings starting Wednesday morning.
Areas east and south of Runyon Canyon in the Sunset fire zone are also under an evacuation warning. In the Hurst fire area, an evacuation warning has been issued for Olive Lane in the Oakridge Mobile Home Park, according to the Los Angeles Fire Department.
Several neighborhoods in Malibu are also under evacuation warnings, according to the city.
The areas include Carbon Canyon, Carbon Beach East, La Costa Beach/La Costa (hillside), Las Flores Creek, Las Flores Mesa, eastern Malibu, Big Rock, Las Tunas Beach, Topanga Beach Road, Carbon Beach Terrace, Carbon Beach, Rambla Pacifico, Carbon Beach West/Malibu Beach, Sweetwater Canyon, Sweetwater Mesa, Serra Retreat, Malibu Creek, Cross Creek, Malibu Colony, Civic Center, Malibu Knolls, Malibu Road, Malibu Country Estates, Puerco Canyon and Piuma Road.
“Residents should prepare to evacuate now due to the significant risk of flash flooding, debris flows and mudslides. These hazards pose a serious threat to life and property,” the city wrote in a post on X.
In the Eaton fire burn scar, officials have warned residents to prepare to leave their homes ahead of the storm.
The city of Sierra Madre issued mandatory evacuation orders for homes directly below the Sierra Madre and Lannan debris basins. Evacuation warnings have been issued for other hillside-adjacent neighborhoods in the community. Those evacuations will remain in effect through 6 p.m. Thursday, according to the city.
Evacuation warnings have also been issued for homes near the San Gabriel foothills in Altadena.
Authorities have visited properties in areas that are at especially high risk to issue specific evacuation orders, according to a news release issued by Mayor Karen Bass’ office on Wednesday.
“While we prepare for another storm headed towards L.A., I want to urge Angelenos to stay vigilant, especially in burn scar areas,” Bass said in a statement.
Evacuations are expected to last until at least Thursday evening.
Officials are concerned that heavy rain overnight could trigger significant debris flows in the burn areas, making it more difficult for people to flee in the dark.
A deadly debris flow in Montecito in 2018 occurred during a storm that brought heavy downpours in the early morning hours when people were asleep. A torrent of mud and boulders was unleashed from the fire-scarred hillsides, destroying homes and killing 23 people.
During this storm, peak rain rates of half an inch to three-quarters of an inch per hour are possible, and there’s a 10% to 20% chance of rain rates that reach an inch per hour if a thunderstorm materializes, according to the weather service. Experts say the risk of mud and debris sliding off burned hillsides rises once rain starts falling at a rate of half an inch per hour.
Los Angeles County officials say they are prepared for the incoming deluge. Crews have reduced the amount of debris in basins so they have capacity to catch mud and other materials that flow off the hillsides during the storm, said Los Angeles County Public Works Director Mark Pestrella.
“All of our debris basins have capacity for this upcoming storm,” he said. “We expect debris and mud to come from slopes without a debris basin below it or from street systems where debris comes onto the street off of the adjacent properties.”
Crews have been hauling debris from a smaller basin — the Sierra Madre dam — every day for the last several weeks. That basin will likely overtop during the storm, as it did during the last major wet weather that hit Los Angeles, Pestrella said.
“In the last event, the flows went over the spillway, ended up in the channel system and flowed safely past homes,” he said. “We expect the same in our model of this event.”
Across Los Angeles County, officials were closing roads because of the risk of damage from the storm.
Pacific Coast Highway between Chautauqua Boulevard in Pacific Palisades and Carbon Beach Terrace in Malibu, and Las Flores Canyon Road and Malibu Canyon Road will be closed at least for the duration of the storm, according to county and state transportation officials.
In Orange County, sheriff’s officials said an evacuation order was set to go into effect at 6 p.m. for areas in Trabuco Creek including the RC Airport, fire station, campground and school; Bell Canyon including Starr Ranch; and Hot Springs Canyon including Lazy-W Ranch because of possible debris flows in the vicinity of the Airport fire burn scar. An evacuation warning is in effect for Long Canyon and Modjeska Canyon.
In San Bernardino County, officials issued evacuation warnings for the area of Wrightwood from the county line east to Pine Street, Rivera Drive south to Acorn Trail and the entire community of Mt. Baldy Village. Residents in the area of Highland adjacent to the Line fire burn zone have also been warned about the risk of debris flows and should be prepared to evacuate, according to the San Bernardino County Sheriff’s Department.
The storm is also expected to drop a fresh dusting of powder across California’s mountain ranges, a welcome boost to the state’s snowpack after a warm, dry start to winter.
As of Wednesday, the statewide snowpack — which provides roughly a third of the state’s water supply — is 81% of average.
In Los Angeles, Ventura and Santa Barbara counties, snow levels will fall to 3,000 feet by Wednesday night, bringing at least light snow to those areas.
One to 2 feet of snow is expected at elevations above 6,500 feet, while 6 to 12 inches could fall at lower elevations. Between an inch and 5 inches is forecast for elevations between 4,000 and 5,500 feet. Winds could gust as high as 50 mph. Officials plan to issue a winter storm warning between 4 p.m. Wednesday and 5 a.m. Saturday.
There’s a risk of blowing snow and ice on Interstate 5 in the Tejon Pass that could cause travel delays. Highway 14 in the Antelope Valley and Highways 33 and 154 could also see issues.
Mountains in San Bernardino and Riverside counties could see accumulations of 4 to 8 inches at elevations between 5,000 and 6,000 feet and 8 to 14 inches at 6,000 to 7,000 feet. Higher peaks, above 8,000 feet, could get 24 inches or more.
In the San Diego County mountains, total accumulations of 4 to 8 inches are expected at elevations above 5,000 feet.
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Another storm system, though much weaker, is expected to move over the region Friday, bringing another chance of drizzly weather to Los Angeles before sunshine returns over the weekend.
But don’t stash those umbrellas away for long. More rain could be on the horizon next week as another storm system moves into Southern California.
Times staff writer Karen Garcia contributed to this report.
