2 Atmospheric Rivers To Hit SoCal: How Much Rain To Expect

LOS ANGELES, CA —A pair of atmospheric rivers are expected to deliver much-needed rain to drought-stricken Southern California this week, and the good news is, there's little chance the first storm will pose hazards for areas recently scarred by wildfires.

Dense fog gathered in the skies over some of the Southland early Monday morning as the region prepared for cooler temperatures and rain. Precipitation will arrive just days after the devastating Palisades and Eaton fires were contained. The wildfires, which killed at least 29 people, burned for nearly a month.

Rainfall from an atmospheric river system that dumped rain in Northern California on Monday is expected to arrive in SoCal as early as Tuesday. But that system is expected to weaken significantly by the time it reaches Los Angeles County, and forecasters believe there is little risk that the rain totals will be enough to reach burn scar thresholds to cause debris flows.

Later in the week, a second storm is expected to bring "more impact, particularly for LA County, compared to the first system" on Thursday and Friday, Rose Schoenfeld, a meteorologist with the National Weather Service told the Los Angeles Times.

The incoming parade of storms will be just the second significant rain event since winter began. The Southland just recorded its driest start to a rainy season in modern history, weather experts told Patch.

The NWS said there is "high confidence in widespread periods of rain in the Tuesday through Friday" period. Early estimates suggest most areas will see moderate rainfall, with about an inch in coastal and valley regions and two to three inches in the foothills and mountains. Forecasters said the upcoming storm will see snow levels at or above 8,000 feet.

Throughout the rainy week, Schoenfeld said that forecasters are expecting some amount of mudslides and road erosion, particularly in "sensitive" canyon roads. But there is only a 5% chance that the rain could trigger significant mudslides or debris flows, the NWS said.

Nonetheless, LA County officials are preparing for the potential of hazards.

"Los Angeles County has been working around the clock to prepare for this storm, clearing debris basins, reinforcing infrastructure, and making sure our residents have the resources they need to stay safe," said Supervisor Lindsey Horvath, whose Third District includes the Palisades Fire area. "I want to thank all of our emergency response teams for their tireless work to protect our communities. I urge all residents to take this time to prepare — secure your property, use sandbags where needed, and stay informed as the storm approaches."

The peak of the first storm will be between Tuesday at 10 p.m. and Wednesday at noon in LA County, which is expected to get between one-quarter to an inch of rain. In the Inland Empire, the storm is expected to rain Tuesday through Thursday. In San Diego and Orange counties, intermittent rain was expected from Tuesday to Friday night.

"For Tuesday evening through Thursday evening, there is a 10 to 20% chance of rainfall accumulations exceeding an inch in the San Bernardino Mountains and a 30 to 40% chance of rainfall exceeding .5 inches for areas (immediately) north of San Diego County," the NWS said in a statement.

Mountain areas across the region could potentially see more rain, forecasters said.

The Southland experienced its first significant winter storm in late January. The L.A. Basin saw accumulations ranging from half an inch to 1.5 inches, while downtown Los Angeles recorded a total of 0.54 inches of rain.

Although the storm spared recent burn areas in Pacific Palisades and Altadena from the heaviest rainfall, it still caused issues. There were reports last Monday of minor mudflows brought on by the rain, including a slide that closed Topanga Canyon Boulevard at Pacific Coast Highway. Lingering snowfall also forced a roughly 11-hour closure Monday of the Grapevine stretch of the Golden State (5) Freeway in northern Los Angeles and southern Kern counties.

Although there's a small risk that this week's rains could cause hazards in burn-impacted areas, the storms are expected to bring some reprieve to bone-dry Southern California. The landscapes suffered amid a late onset of La Niña conditions, which was officially declared by the National Oceanic and Atmospheric Administration in January.

La Niña happens when cooler than normal sea surface temperatures are reported in the equatorial Pacific, which tends to tilt the odds toward dryer than normal in SoCal and wetter than average weather in NorCal.

But La Niña isn't predicted to last long this year.

"La Niña conditions are present and are expected to persist through February-April 2025 (59% chance)," the National Weather Service's Climate Prediction Center noted in January.