Southern California’s next challenge is rain in burnt areas, though it should be light this weekend

While Southern California fire services are still on alert for high, dry winds that forecasters say could last for several days, the region may finally see rainfall on Saturday morning, Jan. 25

Some eight months after any significant precipitation, rain could be both good news and bad news. But meteorologists say it is expected to be relatively light and not lead to significant debris flows or mudslides. At least, not yet.

Before that happens, a red flag warning is in effect for Inland Orange County and the Inland Empire until Thursday, NWS meteorologist Alex Tardy said. The region is expected to continue seeing desert-like dryness, with humidity percentages in the single digits. Winds between 25 to 40 mph are expected later in the week.

“We’ve never been in this territory before,” Tardy said. “We’ve never seen a mid-January with these (humidity) numbers. Never.”

The winds will be weaker on Tuesday night and Wednesday morning, around 10 to 20 mph, Tardy said, but there will be poor humidity recovery overnight.

“Even though the winds are going to be light, it’s going to remain very dry, as if it’s daytime in a lot of our foothills and mountains,” Tardy said.

Winds are expected to pick back up on Wednesday evening, with gusts up to 65 mph. Orange, Riverside and San Bernardino counties will not be “out of the woods” until Thursday night, he said.

A red flag warning also was issued for Los Angeles and Ventura counties from Monday night to Tuesday morning.

Forecasters expect to finally see some rainfall on Saturday morning, a welcome reprieve for fire-ravaged Southern California.

But precipitation could bring its own problems, though they are not necessarily expected this weekend.

Scorched land creates a high risk of debris flow, essentially a flood that brings not only water but debris such as downed trees, large rocks and pieces of destroyed structures. The risk is much greater when there is a large amount of rain in a short amount of time.

Areas with burn scars are vulnerable to debris flows, as the scorched soil cannot absorb rainfall. The oils from the plants make the ground hydrophobic and unable to absorb the water, meteorologist Lisa Phillips said.

The weekend’s rainfall will not be a very powerful storm, but rather showers, bringing between one quarter to a half inch of rain across Orange County and the inland region, Tardy said. Los Angeles is only expecting one-tenth of an inch, meteorologist Lisa Phillips said.

Meteorologists say there is little concern for debris flow in the burn areas, but there will be a risk with any larger storms.

The burn scar of the Airport fire, which scorched portions of Orange and Riverside counties this past September, is also at a higher risk of debris flow in significant rainfall. In the Cleveland National Forest, where the blaze initially began, large rainfall could cause storm channels, which are underneath some road systems and campgrounds, to overflow and overwhelm surrounding areas, said Nathan Judy, a spokesman for the forest. Areas nestled between hills at low elevation are most at risk of debris flow.

Gov. Gavin Newsom issued an executive order on Jan. 20 to expedite debris removal to reduce the risk of debris flows in the widely destructive Palisades and Eaton fires.

“Crews are removing loose debris, fallen trees, and other potential hazards from burn areas,” Los Angeles County Public Works spokesperson Lisette Guzman said in a statement. “Debris basins designed to intercept mudflows in the fire areas are being cleaned and prepared before the rain comes.”

The department is also using sandbags and K-rails to protect infrastructure and divert runoff from burned properties from entering the storm drain system, she said.