Monster storm bears down on California

California girded Sunday for a “potentially historic” storm that put much of the state on high alert, with officials expecting life-threatening damage and issuing evacuation orders or warnings in parts of Los Angeles, Ventura, Santa Barbara and Monterey counties.

“This storm is predicted to be one of the largest and most significant in our county’s history, and our goal is to get through it without any fatalities or any serious injuries,” Santa Barbara County Sheriff Bill Brown said at a briefing Saturday.

This storm could surpass the effects of a powerful storm that hit Jan. 9, 2023, said David Neels, the Montecito fire chief. That event forced the mass evacuation of Montecito, flooded Santa Barbara and left U.S. 101 covered with mud, forcing its closure. It caused more than $80 million in damage to Santa Barbara County, Brown said.

“Our slopes are saturated once again,” Neels said, adding that geologists are warning about the potential for landslides from this storm. “The likelihood of sediment mobilization is real.”

Brown said 6 to 12 inches of rain is expected for Santa Barbara County’s mountains. “But more concerning is the projected duration and sustained amount of rain that we can expect this weekend,” he said.

“Unlike the rain that caused [last year’s Jan. 9] debris flow, for example, the intensity of this storm’s rain is not expected to exceed an inch or an inch and a quarter per hour. It’s just that the rainfall will be far more sustained, over a more or less continuous period for 24 hours or more,” Brown said. “We’re anticipating the possibility of flooding of streets and neighborhoods and of our highways and freeways.”

Los Angeles issued an evacuation warning for about 50 homes and businesses along a section of La Tuna Canyon Road in Sun Valley on Saturday just before midnight, around where McDonald Creek drains into La Tuna Canyon. The county Department of Public Works warned that heavy rain would bring significant flooding and mudflows to the area.

The National Weather Service said there was a “high risk for flash flooding,” a designation used only a few times a year anywhere nationwide, meteorologist Ariel Cohen said at the briefing.

“About half of flood-related deaths occur in high-risk areas. This includes all of the Santa Barbara area, all the way to Los Angeles. This is a particularly dangerous situation,” Cohen said. “I can’t stress enough the importance that everyone be at a very high state of readiness. Take those precautions to save your life from the upcoming floodwaters that will affect the Santa Barbara area.”

The National Weather Service issued an extraordinarily rare “hurricane force wind warning” overnight just off the Central California coast, stretching from the Monterey Peninsula, past Big Sur, to the northern edge of San Luis Obispo County. There hasn’t been a hurricane force wind warning issued off the California coast for at least decades, the weather service said.

A tornado or two are possible in the San Francisco Bay Area, as well as in Santa Cruz, Monterey and San Benito counties.

The storm was hitting the San Francisco Bay Area and the Central Valley earlier Sunday, but the most significant rainfall totals are expected in Southern California and on the Central Coast, National Weather Service meteorologist Eric Schoening said at a separate briefing Saturday.

Los Angeles County, as well as Ventura, Santa Barbara and San Luis Obispo counties, were designated as having the highest weather risk level — extreme, colored in purple, the worst on a five-level scale. Forecasters said there was a 40%-to-70% chance of life-threatening and damaging flooding in those areas.

Heavy snowfall is expected for the mountains, Schoening said, and gusts are expected to down trees and power lines.

“These next storms are going to be impactful and dangerous, and most of the damaging impacts most likely to our coastal and southern regions in the state,” said Nancy Ward, director of the California Governor’s Office of Emergency Services, at the briefing. Storms are “the most dangerous natural disasters that we have — killing more people ... than wildfires every year.”

Ward urged that people avoid nonessential travel during the storm’s peak.

“Don’t walk, swim or drive through flooded waters,” Ward said. “Six inches of water can down an adult in that water. Twelve inches of water can sweep away your vehicle.”

Five rivers in California are anticipated to hit the flood stage: the Ventura River in Ventura County, the San Diego River in San Diego County, the Guadalupe River in Santa Clara County, the Carmel River in Monterey County and the Russian River in Mendocino County, said Karla Nemeth, director of the California Department of Water Resources.

There are also 16 river systems that could hit flood monitor stage. In the Central Valley, reservoirs were already starting to drain stored water downstream to make way for incoming floodwaters, Nemeth said.

The powerful storm is arriving through an atmospheric river, a long plume of water vapor that pours into California from the Pacific Ocean. It carries so much water that it’s likened to a river in the sky.

Here’s a more detailed look at the forecast by region.

Los Angeles, Ventura, Santa Barbara and San Luis Obispo counties

Risk level: Extreme (worst level on a five-point scale).

Peak timing of storm: Sunday through Monday. Very heavy rain is forecast in L.A. County between Sunday evening into Monday morning; in Ventura County, between midday Sunday through Sunday night; and in Santa Barbara County, between Sunday morning and Sunday night.

In a briefing, meteorologist Robbie Munroe called incoming system a “potentially historic storm.”

“It looks like ... the worst rainfall and wind really is in that Sunday-to-maybe-Sunday-night time frame. But following that very heavy rain and very wet conditions, any additional rainfall Monday, Tuesday and even beyond really exacerbate things,” Munroe said.

On Sunday, there’s a “high risk” — at least a 70% chance — of excessive rainfall leading to rapid onset flooding in large portions of Ventura and Santa Barbara counties, and a “moderate risk” — at least 40% chance — of that in a wide swath of northern and western Los Angeles County and coastal San Luis Obispo County.

On Monday, there’s a “moderate” risk of excessive rainfall in eastern and southern L.A. County.

Rainfall forecasts: Astonishing amounts of rain were forecast across urban L.A. County through Tuesday, including about 4 inches in Long Beach, Redondo Beach and Oxnard; about 5 inches in downtown Los Angeles and Pomona; and 6 inches in Northridge, Santa Clarita and Santa Barbara.

“Especially with the recent rains, we can expect widespread flooding issues in and around the L.A. area,” Munroe said.

In the Santa Barbara County mountains, Big Pine Mountain could get nearly 10 inches of rain.

Thunderstorms: There’s a chance Sunday, Monday and even Tuesday.

Peak rainfall rates: It’s possible in some areas, especially south-facing foothills, that 2 to 3 inches of rain could fall within three hours. If that happens, that “could be a huge problem,” Munroe said.

Peak winds: Peak wind gusts could hit 40 mph to 60 mph across the region, with gusts of up to 90 mph in the mountains. Officials said to expect delays at airports. Peak winds for L.A. County are expected Sunday afternoon through Monday morning.

Snow: Avalanche potential exists at an elevation of 7,000 feet above sea level, and there’s a heavy snow risk at elevations above 6,000 feet. “Residents might need to be prepared to be stranded for several days,” Munroe said. There could be traffic issues along the Grapevine section of Interstate 5.

Coast: Expect flooded beach areas and coastal erosion and dangerous surf. Residents who live in flood-prone areas should move their cars out of low-lying areas, Munroe said.

Orange, Riverside, San Bernardino and San Diego counties

Risk level: Moderate to minor on Sunday; major to moderate on Monday.

Peak timing: Sunday afternoon through Monday, with moderate rain Tuesday.

Rainfall forecasts: Orange County, as well as the cities of Ontario and San Bernardino, could get up to 5 inches of rain; Riverside could get up to 4 inches; and San Diego up to 3 inches. “Any heavy rainfall that does occur, we will be seeing flash flooding again,” National Weather Service meteorologist Adam Roser said in a video briefing.

Snow: Heavy snow could cause power outages and make traffic difficult in the mountains. Heavy snow could occur down to an elevation of 5,500 feet by Tuesday; areas near 6,000 feet are likely to see 6 inches or more; and nearly one foot of snow is expected between 6,000 to 7,000 feet. There may be areas that get 2 to 3 feet of snow at elevations over 8,000 feet.

Winds: Strong winds could be powerful enough to blow down tree limbs and make driving difficult for high-profile vehicles. In the San Bernardino Mountains into the high desert, there could be gusty winds in excess of 50 mph, and even up to 70 mph, Roser said.

Greater San Francisco Bay Area

Risk level: Extreme in Monterey and San Benito counties on Sunday; major to moderate in the San Francisco Bay Area and Santa Cruz County

Peak timing: Early Sunday into Sunday evening.

Winds: Gusts of above 60 mph are possible; with gusts of more than 75 mph possible in the Santa Lucia Range above Big Sur.

San Francisco International Airport was also expected to be affected by strong winds.

“Loose or unsecured objects may be blown away,” the weather service said in an email. “Strong winds may produce difficult driving for high-profile vehicles.”

Thunderstorms: There increased thunderstorm risk in the South Bay and Central Coast areas. Tornadoes are possible.

Impacts: Downed trees and landslides are possible, including along the River fire burn scar in Monterey County. “People living unhoused along the Guadalupe River will be ordered to evacuate,” San Jose officials said.

Central Valley and Sierra Nevada

Risk level: Major to moderate.

Peak timing: Sunday and Monday. Moderate to heavy rain is forecast for the Sierra Nevada, the Sierra foothills and the Kern County desert. The winter storm “could easily be the strongest of the season,” the weather service office in Reno said.

Impacts: Flash flooding and landslides are possible, and travel will be difficult. “Gusts of up to 80 mph are conceivable along the Grapevine” section of Interstate 5, the weather service said. “Avoid large trucks and tractor trailers, slow down, and hold on to the steering wheel with both hands.”

As for the Sierra Nevada, “we still have high confidence in major snow impacts and whiteout conditions,” wrote weather service meteorologist Brian Brong. Forecasters warned of “near impossible mountain travel” Sunday into early Monday.

An avalanche watch was issued by the Eastern Sierra Avalanche Center