Two rounds of rain expected to hit Southern California: What to know

An atmospheric river storm that dumped record rain in Northern California is bringing decidedly less precipitation to Southern California.

“The whole thing weakened and moved down the coast,� said Joe Sirard, meteorologist with the National Weather Service in Oxnard. “This is its last gasp.�

Rain moved into San Luis Obispo, Santa Barbara and Ventura counties Saturday morning and was expected to reach Los Angeles County by midday.

Los Angeles and Ventura counties could see anywhere from a tenth to a third of an inch of rain. San Luis Obispo and Santa Barbara counties could see up to an inch in some areas — with the exception of an area in the hills of far northwestern San Luis Obispo County, where the Rocky Butte weather station had already recorded over three inches of rain by 9 a.m., Sirard said.

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A second round of rain was expected to begin Sunday in San Luis Obispo and Santa Barbara counties and then move south, potentially reaching Los Angeles County by Sunday night or Monday, when there is a 40% to 50% chance of more rain, Sirard said. Showers could linger to Wednesday, he said. There is also a slight chance of rain over San Luis Obispo County on Thanksgiving Day, he added.

That second storm system could produce rainfall totals of half an inch to an inch for San Luis Obispo and Santa Barbara counties; a third to a half an inch for Ventura County and a tenth to a quarter of an inch for Los Angeles County.

Chances are low of dangerous flooding or any other significant issues in Southern California, forecasters said, though roads could become slick and snarl traffic.

Concern about the upcoming rainy season has been growing among residents living on and near the Portuguese Bend landslide area in Rancho Palos Verdes, because increased rainfall leads to more groundwater — which is the impetus for the ongoing devastating land movement.

But city officials are hopeful that extensive “winterization efforts,� which include improving drainage, filling in cracks and lining canyon walls, can help minimize the effect of any new rain. Many of those projects have been completed, but some remain underway. The work aims “to best prepare ourselves for the wet weather season ahead,� said David Copp, the city’s deputy public works director.

Parts of the landslide have seen recent slowing, and, in some areas, even complete stabilization, the city has reported, but additional rain is always a concern for this unstable region.

In Northern California, the storm brought several feet of snow in the Sierra as well as flooding and the threat of mudslides.