‘Dangerous scenario unfolding’ in Southern California from potent storm lashing the entire state

CNN

By Meteorologists Mary Gilbert, Chris Dolce, Andrew Freedman, CNN

(CNN) — A powerful storm carrying a strong atmospheric river is laying siege to California, where evacuations have been issued because of the risk of life-threatening flooding and debris flows.

“A dangerous scenario is unfolding, with widespread and significant impacts from flash flooding and debris flows expected,” the Weather Prediction Center said about areas near and north of Los Angeles as the downpours arrived Wednesday morning.

Some areas in the mountains to the north and northwest of Los Angeles have already seen 4 to 8 inches of rain and the atmospheric river continues to soak the region. Feet of mountain snow, severe thunderstorms and strong winds round out the multiple threats the state is facing.

Evacuation warnings or orders were in place in parts of at least five Southern California counties, notably around areas recently burned by wildfires.

California Gov. Gavin Newsom declared a state of emergency in Los Angeles, Orange, Riverside, San Bernardino, San Diego and Shasta counties. The state of emergency will “activate emergency authorities and preposition resources to keep our communities safe,” Newsom said in a Wednesday post on X.

Here’s the latest:

• Rare high risk of flooding rain: More than 7 million people in portions of Los Angeles, San Bernardino, Ventura and Santa Barbara counties are in the highest-risk zone Wednesday, according to the Weather Prediction Center. More than a dozen flash flood warnings have been issued this morning in Southern California. One of those includes over 6 million people in Los Angeles until 6 p.m. PT.
• Roads and highways washed out: Authorities in northwest Los Angeles and northeast Ventura counties have reported “heavy rain, rockslides, mudslides, and washed out roadways,” the National Weather Service said. Debris flows and flooding have also been reported in the San Bernardino Mountains, including Highway 2. Mud and debris flows shut down northbound Interstate 15 near Cajon Junction Wednesday morning, according to Caltrans. Law enforcement has also reported flooding across nearly all lanes of Interstate 5 just northwest of Burbank, the NWS said. The Los Angeles Police Department has responded to 52 traffic accidents, a Wednesday morning release from the mayor’s office said.
• Rescues underway amid mud and debris flows in Wrightwood: The San Bernardino County Sheriff’s Dept. issued a shelter-in-place order for the community of Wrightwood, northeast of Los Angeles, Wednesday afternoon due to flash flooding, mud and debris flows. An evacuation warning was previously in effect for the area. Video posted by the county Fire Department showed heavy flooding in the area that made Highway 2 impassable.
• Man rescued on Los Angeles River: The Los Angeles Fire Department rescued a man trapped in a small drainage tunnel on the Los Angeles River in the Winnetka neighborhood during heavy rain Wednesday morning. Two other people in the area were also moved out of the danger zone, the department said. The fire department has deployed teams to two river rescue incidents as of early Wednesday afternoon, the mayor’s office said.
• Thousands without power amid high winds: Strong winds and heavy rain blasted Northern California this morning, including the Bay Area, where a wind gust up to 108 mph was clocked in the northern hills. Wind gusts have topped 90 mph in multiple spots across Southern California’s San Gabriel Mountains. Around 110,000 homes and businesses have lost power in the state, according to PowerOutage.us.
• Chain controls in effect for I-80: The snowy side of this storm is now ramping up in the Sierra Nevada. Requirement 2 chain controls are in effect for Interstate 80, which means chains or traction devices are required on all vehicles except those with four-wheel or all-wheel drive that also have snow-tread tires.
• Driver killed after wet roadway crash: A motorist crashed and died on a wet roadway in South Sacramento, California, the state highway patrol told CNN. “While the crash is still under investigation, it appears that the vehicle was traveling at an unsafe speed on the wet roadway and lost control,” hitting a metal power pole, the agency said. Heavy rainfall had occurred in the 5 a.m. hour and light rain was in the area during the time of the crash.

Rare high risk on Christmas Eve

High risk flooding events are incredibly significant: High risks are issued on fewer than 4% of days per year on average, but are responsible for more than 80% of all flood-related damage and 36% of all flood-related deaths, WPC research shows.

Rainfall rates could exceed 1 inch per hour at times Wednesday. That’s more than enough to trigger dangerous flash flooding and life-threatening debris flows on recent burn scars, including from January’s Eaton and Palisades fires.

The scorched ground of these scars repels water instead of absorbing it, quickly turning rain into a surge of floodwater that pulls mud and debris with it.

The holiday danger doesn’t end Wednesday: Another atmospheric river-fueled storm will follow Christmas Day and continue into Friday. It’s raising a Level 3 of 4 flooding rain risk for more than 12 million people, including many in Wednesday’s high risk.

All told, rainfall totals in Southern California through the end of the week could be as much as 4 to 7 inches in coastal and valley locations, while foothills and mountains see 6 to 14 inches.

To put those totals into perspective, a city like Los Angeles could see anywhere from two months’ worth of rain to nearly half a year’s worth in just a week.

Residents not evacuating despite orders

Ventura, Santa Barbara, Orange and San Bernardino counties all issued evacuation warnings or orders for the threat of flooding by Tuesday evening. They join orders and warnings first issued on Monday by Los Angeles County for areas in and around burn scars in the greater Los Angeles area, including the Eaton and Palisades fire zones.

The orders in the Los Angeles area for 383 properties that sheriff’s deputies reached out directly to, including going door-to-door, the county Office of Emergency Management said Monday.

But many of the people had chosen not to leave, the city’s Police Chief Jim McDonnell said at a Tuesday news conference.

“I would ask you to seriously reconsider that,” McDonnell said.

They include Steve Schklair and his family, who live in a warning area for debris flow and mudslides, recently moved back into their home in Altadena, which they spent almost a year rebuilding following the fires, he told CNN affiliate KCBS.

But the family will not be evacuating because they live in a “lucky spot” and will instead spend Christmas hunkered down at home, Schklair said.

“All the mud flows — and it does flow — (go) around the house and down the street, never comes up here,” he told KCBS.

Impossible travel conditions in the mountains

Feet of snow falling in the Sierra Nevada will make travel there difficult or impossible at times through Friday. That includes Interstate 80 through Donner Pass.

The heavy snow will be a big change for the region, which has had much less snow than usual to start the season.

If that’s not enough, severe thunderstorms are a threat for coastal parts of California both Wednesday and Thursday. Any storms that turn severe could produce damaging wind gusts or a brief tornado.

Some relief from this nonstop stormy pattern looks to finally arrive for the upcoming weekend.

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CNN’s Eric Levenson and Cindy Von Quednow contributed to this report.