LOS ANGELES _ Heavy rain that pounded Los Angeles and the surrounding areas early Thursday caused debris to flow onto Pacific Coast Highway in Malibu and prompted the National Weather Service to issue a flash flood warning for Los Angeles and Ventura counties.
Pacific Coast Highway is closed from Busch Drive to the Ventura County line after mud flowed onto the roadway. A thick layer of mud caused at least one vehicle to get stuck.
Mudslides also were reported on Kanan Road and in the 30400 block of Morning View Drive in Malibu, according to the Los Angeles County Sheriff's Department.
Rain that rolled into the area overnight and continued into Thursday morning proved to be more significant than the scattered showers from the previous day, said Keily Delerme, a meteorologist with the National Weather Service.
"Yesterday, the difference was we had east winds that were drying things out, so not much rain was falling," Delerme said. "Today, those winds have weakened, and it's allowing for more rain to fall."
Shortly after 6 a.m., the Woolsey and Hill burn areas were seeing a quarter of an inch to nearly half an inch of rain per hour. Those amounts were just under thresholds that could trigger debris flows, Delerme said.
But the rain continued to drop with ferocious intensity. About a third of an inch of precipitation fell on the Woolsey and Hill burn scar areas in about 30 minutes shortly before 8 a.m., according to the weather service, which warned that debris flows "are expected to begin shortly."
No evacuation orders have been issued.
The soil in burn areas cannot absorb a lot of moisture, so heavy rainfall can lead to fast-moving flows containing mud, debris and even trees and boulders. When rain falls over time, it can be gradually absorbed or dispersed, but when areas see rapid runoff, entire hillsides can come down without warning, sometimes with deadly results.
The National Weather Service said residents should be on alert for possible rock slides and minor debris flows, especially across Highway 1, Kanan Road, Malibu Canyon and near canyon roadways affected by the recent wildfires.
A deluge during the morning commute caused spin-outs and dozens of crashes on freeways. A portion of the southbound 170 Freeway near Victory Boulevard in North Hollywood closed shortly before 7 a.m. after mud flowed onto the roadway, according to the California Highway Patrol. It is not clear when the freeway will reopen.
The storm, which is expected to linger through early Friday, will drop up to an inch and a half of rain on much of the region. Mountain areas probably will see a bit more precipitation. There's also the possibility the system could bring isolated thunderstorms along the coast by Thursday afternoon, Delerme said.
A storm affecting Southern California last week, which prompted evacuations and dumped a significant amount of water, triggered mud flows near the Holy fire burn area. The rain also caused some rock slides and road closures in Malibu.
Orange and San Diego counties, which received fairly steady showers on Wednesday, were not seeing as significant rainfall Thursday morning. The area could see more scattered showers later in the day, said Greg Martin, a meteorologist with the National Weather Service.
Rainfall rates are not expected to trigger debris flows in the Holy fire area, but forecasters are continuing to keep an eye on the situation through the day, Martin said.
