A major storm is poised to bring months of rain and strong winds to Southern California. It is the most powerful of the massive atmospheric river storms targeting the region this week.
The heatwave comes on the heels of a storm that left at least one person dead and caused severe flooding in Northern California over the weekend.
A new storm was gaining strength over the Pacific Ocean early Tuesday morning. Rain and wind will begin hitting the entire California coast from north to south late Tuesday night.
Heavy rain began falling in Southern California early Wednesday morning and is expected to continue into the evening.
A “high” risk level for flooding rain was in effect Wednesday for the region, which includes parts of Los Angeles, San Bernardino, Ventura and Santa Barbara counties with a population of about 6 million people, according to the Weather Prediction Center.
These high-risk flood events are extremely serious. Although high-risk days occur on average less than 4% of the year, they are responsible for more than 80% of all flood-related damage and 36% of all flood-related deaths, WPC research shows.
Wednesday’s high risk is the first in Southern California since Feb. 5, 2024, when catastrophic flooding killed at least two people and caused more than 100 landslides.
The National Weather Service in Los Angeles warned early Tuesday that “widespread, major urban flooding is likely, along with rock, mudslides, and debris flows,” noting that these threats are not limited to burned areas.
“This is a very dangerous holiday storm,” the NWS continued. “People traveling on Christmas Eve or Christmas Day should take extreme caution.”
California Gov. Gavin Newsom mobilized state resources ahead of the holiday week storm, with government agencies deploying crews and equipment in advance, the governor’s press office said.
Rainfall could exceed 1 inch per hour during the early morning hours Wednesday, especially in mountainous areas of Santa Barbara and Los Angeles counties. This is more than enough to cause dangerous flash flooding and potential landslides.
Recent burn scars, such as the Eaton and Palisades fires in January, can generate life-threatening debris flows, and heavy rains can trigger debris flows. The scorched ground in these scars repels water rather than absorbing it, quickly turning rain into floods and pulling mud and debris along with them.
Los Angeles County on Monday announced evacuation orders and warnings for areas around burn scars in the greater Los Angeles area, including the Eaton and Palisades fire zones. The deadly fires were two of the most destructive fires in California history, with a combined 16,246 structures destroyed, according to CalFire.
The county Emergency Management Agency announced Monday that the order is for 383 facilities that sheriff’s deputies are contacting directly, including door-to-door visits. These evacuation alerts go into effect Tuesday morning at 11 a.m. PT.
Evacuation warnings were also issued for parts of Ventura County, and an evacuation order was issued for the Ventura Beach RV Resort Tuesday at 6 p.m. Evacuation orders are also in place for parts of Santa Barbara County, including some areas within the Lake Fire burn scar.
Strong winds can bring down trees and power lines, adding to the danger. Winds will be heaviest in the region’s mountainous regions, with sustained winds from the south between 30 and 50 mph, with gusts as high as 80 mph possible.
That’s not the only danger of the holidays. Another river-driven storm will continue Thursday into Friday.
Overall, precipitation totals for Southern California by the end of the week could reach 4 to 8 inches along the coast and in the valleys, and 8 to 12 inches in the foothills and mountains.
To put these totals into perspective, a city like Los Angeles can receive anywhere from two months to almost half a year’s worth of rain in just one week.
The abundant moisture hitting Southern California will also bring several feet of snow further north to the Sierra Nevada mountains, making travel there difficult or impossible at times.
The heavy snowfall will be a big change for the region, which started the season with far less snow than usual.
This persistent storm pattern finally looks like there will be some relief next weekend.
