Steady rain fell across much of Los Angeles County Monday morning as a three-day storm arrived, accompanied by numerous flash flood warnings and at least one evacuation warning as authorities urged caution on area roads.
Forecasters reported rainfall rates of 0.10 to 0.25 inch per hour, but nearly a half-inch per hour in the Santa Monica Mountains, which had already received 3 inches of rain by Monday morning.
Flash flood warnings and flood advisories were in affect through Wednesday morning over much of Los Angeles County, and the National Weather Service said “there have been many reports of rockslides, mudslides and flooded roads” Monday in Santa Barbara, Ventura and Los Angeles counties.
An evacuation warning was issued along Santa Maria Road north of Topanga Canyon Boulevard, southeast of Calabasas, due to possible mud/debris flows from 9 a.m. Monday through 9 a.m. Wednesday.
LA County Public Works officials issued a “phase 2 debris flow forecast” for the Land Fire burn area east of Sun Valley. The alert will be in effect from 9 a.m. Monday to 9 a.m. Wednesday, according to the Los Angeles Fire Department, which said moderate flooding and mudflow/sediment deposition should be anticipated in the area of McDonald Creek, Del Arroyo Drive and La Tuna Canyon Road.
“If conditions worsen, evacuation orders may be issued and evacuation sites will be identified,” the LAFD said. “Take action now to be ready to quickly evacuate if you live on the streets along La Tuna Canyon Road with the borders of Horse Haven Street to the north, Martindale Avenue to the east, Penrose Street to the south, and Ledge Avenue to the west.”
Farther south, a portion of Benedict Canyon Road was restricted to local access only due to a collapsing roadway. The “soft closure” was in effect from Mulholland Drive to Hutton Drive, with Deep Canyon Drive suggested as an alternate route.
A portion of Mulholland Drive remained closed to through traffic between Skyline Drive and Bowmont Drive due to severe road damage at four locations. That closure was expected to last weeks, officials said.
And the Skirball Center Drive/Mulholland Drive off-ramp from the northbound San Diego (405) Freeway was closed until further notice due to a sinkhole.
Flood fears are heightened due to the region’s already soaked terrain from storms earlier this year, prompting Los Angeles city officials to put comprehensive measures in place to manage the effects of the latest storm.
“Over the past week, the City has worked to repair more than 4,000 potholes, reinforce hills that are at risk of mudslides and prevent power outages by making repairs to underground equipment and vaults that had flooded during the previous storm,” Mayor Karen Bass said Sunday on X.
Gov. Gavin Newsom activated the State Operations Center to help coordinate state, local and federal response to the storm.
The storm is also expected to produce high surf and gusty winds in the mountains and foothills. Snow levels during the peak of the storm will be about 8,000 feet, lowering to around 7,000 feet Monday or Tuesday, with 5 to 10 inches possible between 6,500 and 8,000 feet.
A high surf advisory will be in effect through 10 p.m. Tuesday in coastal Orange County, with waves up to 10-15 feet expected, and a coastal flood advisory is in effect until 9 a.m. Tuesday at Catalina Island.
A wind advisory was in effect until 6 p.m. Monday in the San Gabriel Mountains and the Antelope Valley, where gusts of 56 mph were expected.
Dry weather with warming temperatures is expected to return Thursday and Friday, before another bout of light rain next weekend.