New California storm triggers flash flood warning for western L.A. County

Rain rolled into Los Angeles County on Monday and was expected to continue through Wednesday, with the latest storm system bringing heavier precipitation and a threat of flash flooding to western Los Angeles County and swaths of Ventura County.

A flash flood warning was in effect Monday for a large portion of western L.A. County, including the Santa Monica Mountains, extending eastward to Hollywood Hills and Griffith Park. Other areas affected by the flash flood warning included surrounding areas in Malibu and the San Fernando Valley.

Around 11 a.m., radar indicated light and moderate showers over that area, and “heavier showers will overspread the warned area through the day. Law enforcement has already reported landslides occurring across the warned area,” the weather service said.

About 9:30 a.m., there were reports of a mudslide blocking the westbound lanes of Pacific Coast Highway near Santa Monica; another mudslide covering one lane of U.S. 101 near La Conchita in Ventura County; and large boulders blocking both lanes at the intersection of Malibu Canyon and Piuma roads north of Malibu.

Officials reported flooding on the Refugio Road offramp near U.S. 101 in Santa Barbara County, close to Refugio State Beach, and “several vehicles were stuck in the flooded roadway,” the weather service said.

There were earlier reports of flash flooding and landslides in Ventura and Santa Barbara counties Monday morning.

In Santa Barbara, where up to 10 inches of rain fell by noon, a body was discovered in Mission Creek in the city’s downtown. It was unclear whether the death was related to the storm, and an investigation was underway, a police spokesman said. Santa Barbara Airport was closed Monday morning due to flooding.

There were reports of two lanes of U.S. 101 in Ventura shut Monday morning because of flooding, the weather service said.

There were also reports of flooded roads in San Luis Obispo and Santa Barbara counties, including a large fallen tree and heavy mud that flowed on sections of Highway 192 in and near the foothill areas of Santa Barbara, Montecito and Carpinteria.

Heavy rainfall rates were reported in parts of Ventura County, of up to 0.75 inch per hour.

Compared with the historic storm that pummeled the region earlier this month, forecasters expect “much less rain” for Los Angeles County this time but warned that the most intense precipitation of the storm was expected during the day Monday and Tuesday night. Over the next three days, downtown could see up to 2.4 inches of rain; Santa Clarita, 2.19 inches; Long Beach, 1.8 inches; and Torrance, 1.97 inches.

The rain may not be as intense as some areas farther north, but there are still concerns about the prospect for flooding, landslides and mudflows — particularly in the Santa Monica Mountains and Hollywood Hills — because of the soaking Southern California received from the previous storm, David Gomberg, a weather service meteorologist in Oxnard, said during an online media briefing.

“Debris flows, mudslides and landslides could happen just about anywhere within the flood watch area, as even L.A. County — which is expecting somewhat lower rainfall totals — took the brunt of the last storm, leaving them more susceptible to this kind of activity,” the weather service office in Oxnard said Sunday night.

Residents are urged to move parked cars out of low-lying flood-prone areas, to be alert for mudslides and rock slides on or below canyon roads and to prepare for possible flooding and power outages, the weather service said.

The slow-moving storm system began moving into the Central Coast region Saturday night, bringing light rain to Santa Barbara and western San Luis Obispo counties, officials said. The second, more powerful wave of the storm had arrived in Santa Barbara by Sunday evening. Officials warned of gusty winds, an increased chance of thunderstorms and the possibility of high surf and coastal flooding.

The Central Coast is expected to feel the brunt of this storm, according to the weather service. Santa Barbara and San Luis Obispo county foothills and mountain ranges could see 8 to 10 inches of rainfall. The city of Ventura can expect to see up to 3.01 inches, and the city of Santa Barbara 5.66 inches.

High surf advisories are in effect through Tuesday across all beaches in the region, with waves of up to 20 feet expected in some areas. Strong rip currents are expected with large breaking waves at Morro Bay, Port San Luis and Ventura harbors.

There is also a brief risk of “weak tornado activity” during this period in San Luis Obispo County, Gomberg said Sunday.

The greatest threat for coastal flooding — particularly in Malibu and Santa Barbara — will be Tuesday morning, Gomberg said.

The engine driving the storm system across the central Pacific is the jet stream — high-altitude winds in excess of 200 mph — which is expected to slow as it approaches the coast.

Once the system has passed, the state will have a few days to wring itself out before the arrival of another possible system next weekend, Gomberg said, this time coming out of the north and potentially colder.

Times staff writer Thomas Curwen contributed to this report.