The strongest storm so far this winter is expected to make landfall in Southern California toward the end of the week, bringing with it a heightened concern about mudslides, debris flows and flooding.
An up to 80% chance of moderate to heavy rain in the region is expected on Thursday and early Friday, following a 20-40% chance of light rain beginning on Wednesday, Feb. 12, the National Weather Service said.
“This looks to be the first significant rainfall event of the winter season,” NWS meteorologist Adam Roser said.
Los Angeles is likely to bear the brunt of the rain compared to Orange County and the Inland Empire, which raises concerns about large amounts of sustained rainfall triggering mudslides, flooding and other problems in the burned areas of the Palisades and Eaton fires.
The storm system could bring 2 to 4 inches of rain or more along the coast and in the valleys and 4 to 8 inches or more in the mountains and foothills, Meteorologist Bryan Lewis said.
“There is at least a moderate risk for widespread heavy rain, significant flooding, debris flows, high elevation mountain snow and strong winds,” the NWS said.
Moderate rainfall, for which there is a 50% chance, would bring between one-quarter and one-half an inch of rain per hour, for up to a 12-hour period.
There also is a 30% chance of high amounts of rainfall, the NWS reported. That would mean 12 to 24 hours of rain at a rate of one-half to one inch of rain per hour. That pattern would be most concerning for the burn imprints.
“It really depends on how slow this storm moves,” meteorologist Kristan Lund said.
The predictions could change during the week as the storm approaches.
The biggest concern is substantial rainfall focused on a particular area, such as a thunderstorm.
“Right now, we’re thinking there’s a 5% to 10% chance of thunderstorms. The risk is still not extremely high, but it’s higher than the last event,” Lewis said, referring to the past week’s storm system.
The rain, which largely let up early Friday, led to wet roads, a mudslide on Pacific Coast Highway and some rocks tumbling near Pacific Palisades, but no major damage overall.
The mudslide on PCH just north of Big Rock Drive covered all lanes of the roadway — which was closed at the time as a storm precaution. Caltrans officials said crews were examining the damage, and it was unclear how long it would take to clear the road.
PCH will remain fully closed between Carbon Beach Terrace in Malibu and Chautauqua Boulevard in Los Angeles until further notice, according to Caltrans. The closure is for safety in case of more debris slides and to allow Caltrans and Los Angeles County crews to remove debris, mitigate slope slippage and clear debris basins.
“Malibu residents and essential contractors who previously received PCH access passes will NOT be able to get through the PCH closure,” Malibu officials said.
A little to the east, rocks were reported to have fallen near Sunset and Topanga Canyon boulevards. But no injuries were reported.
Orange, Riverside and San Bernardino counties should expect up to two inches of rain between Wednesday and Friday, Roser said. He said the areas of most concern for flooding, slides and debris flows are those at lower elevations, as well as the burn scars of the Line, Bridge and Airport fires last year.
Residents in vulnerable areas are urged to clear drainage paths around their properties, install sandbags to direct runoff away from homes, and avoid travel in burn areas and mountain roads during heavy rainfall.
City News Service contributed to this report.