A slow-moving storm system settled across Southern California on Sunday, providing a reprieve from a long drying spell but raising the risk of mudslides in areas scarred by wildfires this month.
Showers are expected to continue into Monday afternoon, with bursts of light rain and intermittent heavy rain across the region, forecasters said. The rain could reduce the risk of fires and help vegetation during the driest start to the rainy season on record in Los Angeles.
But the National Weather Service also assessed several burn scars in Los Angeles County, sensitive areas where trees and brush have been swallowed up, to have a 10 to 20 percent chance of massive mudslides.
In burn scars, charred soil can act like slick pavement when soaked by rain, creating conditions for mudslides, said Marc Chenard, a meteorologist with the service.
“You just don’t absorb the water,” Mr. Chenard said. “Everything immediately becomes runoff.”
The service shows the highest intensity of rainfall is expected between 4pm on Sunday and 4pm on Monday. Los Angeles and Ventura counties are expected to receive one inch of rainfall totals, and up to three inches are expected in the mountains near Los Angeles.
Burn scars include areas of the Palisades Fire in Los Angeles’ Pacific Palisades neighborhood; the Hurst Fire near the Sylmar area of the city; the Sunset Fire near West Hollywood; and the Eaton Fire near Pasadena fire; the Hughes Fire near Lake Hughes; and the Franklin Fire near Malibu.
The weather service said Burn Scar outside Los Angeles County has a 5 to 10 percent chance of experiencing a mudslide.
Residents are urged to stock up on supplies and protect property with sandbags. A flood watch is in effect for Los Angeles County until Monday afternoon.
The service said the rain arrived in Ventura County, north of Los Angeles, on Saturday night and was picked up in the area on Sunday.
The system is drifting southeast through Los Angeles County, bringing lightning and hail to some areas, according to the service. By Sunday afternoon, the highest rainfall rates, about three-quarters of an inch, will be limited to isolated areas.
Mr Chenard warned that more than half an inch of rain per hour in burn scars could pose “some significant problems”.
The Los Angeles area has endured months of brutal drought, feeding this month’s devastating wildfires that burned thousands of acres and displaced more than 100,000 people.
Before Saturday, there had been no measurable rainfall in downtown Los Angeles this year, Accuweather senior meteorologist John Feerick said. He described the rain as welcome news.
“Overall, it’s been beneficial rainfall,” Mr Ferrick said. “This should help the fires tremendously.”
He added: “Now, that’s the risk, because of the burning scars.”
