High risk of devastating flooding as atmospheric river hits California -

California is feeling the effects of the historic and potentially deadly storm that is slamming into the western coast, unleashing evacuation orders or warnings and risks of serious and widespread flash flooding, damaging winds, isolated tornadoes and prolific mountain snow.

On Sunday afternoon and evening, 50 to 80 mph winds downed trees onto homes, cars and power lines in the Bay Area and Central Coasts; in the Sierra Nevada some gusts topped 100 mph. Over 900,000 customers in the state were without power around 7 p.m. Sunday local time and officials urged residents to only travel for essential reasons. Winds were blasting the Bay Area and gusted to 77 mph at San Francisco International Airport late in the afternoon.

Flooding was increasing in Southern California, where high water forced the closure of Santa Barbara Airport and the National Weather Service said conditions were poised to deteriorate dramatically overnight.

By 9 p.m. local time, a flow of debris had significantly damaged at least two homes on a Studio City street and forced the evacuation of nine, the Los Angeles Fire Department said, with live footage on CBS News showing fast currents of muddy water ripping through a suburban street and a stray refrigerator tilted over on the road. Firefighters helped evacuate at least 16 people and their pets.

As the storm rapidly strengthened and damage mounted around the state, Gov. Gavin Newsom (D) declared a state of emergency for eight Southern California counties, including Los Angeles, Orange, San Diego and Santa Barbara. Flight delays, diversions and cancellations piled up at San Francisco International Airport and Los Angeles International Airport, according to data from FlightAware, a flight-tracking website.

Around Los Angeles, downpours set records Sunday, and some of the heaviest rain was still to come overnight. The Weather Service office serving the area used dire language to describe the unfolding storm threat.

“This is a DANGEROUS SYSTEM with major risks to life and property,” the office wrote. “Many roads and freeways will flood or shutdown. Canyon roads will experience significant rockslides. Low-lying neighborhoods will see waters over curbs with a foot or two of water into vulnerable homes and businesses. Many parked cars will be damaged. Mudslides will occur over vulnerable areas. Recent burn scars will experience deep debris flows.”

The storm could bring months’ worth of rainfall, warned officials, who are bracing to see double-digit rainfall totals in the mountains north of Los Angeles and east of Santa Barbara. Waves of torrential rain were expected through Monday night, although the heaviest was predicted Sunday night into Monday morning. Flash-flood warnings were issued late Sunday from San Luis Obispo County to Long Beach, including Los Angeles, which saw 1 to 4 inches of rain and was bracing for several inches more, officials said.

“Flash flooding and debris flows are occurring and will worsen tonight,” the Weather Service said.

The Weather Service drew a level 4 out of 4 “high” risk of flash flooding and excessive rainfall between Santa Barbara and Orange counties. Evacuation orders have already been made in Ventura County, where runoff from up to a foot of rain in the mountains will couple with drenching in the lowlands.

Officials also issued preemptive evacuation orders in the Los Angeles area near steep slopes and areas previously burned by wildfires. And, there is growing concern that the atmospheric river will park itself over Southern California, streaming a conveyor belt of moisture over the region.

“This system really could stall out somewhere between Santa Barbara County and Orange County and cause big problems,” UCLA climate scientist Daniel Swain said in an online update Sunday morning.

Most of the California coast is under other flood watches and high-wind warnings or wind advisories. In addition to a widespread 2 to 8 inches of rain from the Bay Area to San Diego, winds gusting to at least 50 to 60 mph at the coast and much higher in the mountains were predicted to batter the region.

The Weather Service had warned gusts could reach 70 to 90 mph for the Big Sur coastal waters, where it issued what appeared to be the first-ever hurricane-force wind warning for the area into Sunday evening. Mountainous areas were also predicted to endure winds to hurricane-force.

The National Weather Service in Los Angeles increased expected rain amounts to 4-8 inches on the coastal plain and 8-14 inches for mountain areas.

Areas farther south, toward San Diego, and east may not see the heaviest rain until Monday into Tuesday.

Strong, rain-filled winds lashed Santa Barbara starting early Sunday morning, roiling the surf and toppling trees whose roots were already loose in saturated soil.

Before dawn, a 70-foot tree fell on a condo complex in the town of Goleta, just north of Santa Barbara and home to many University of California at Santa Barbara students. The trunk crashed through the roof, sending bales of pink insulation into rooms while residents slept, ultimately displacing four people and a dog.

Emergency crews quickly responded and were on-the-go in the hours since, said Scott Safechuck, a spokesman with the county fire department. Throughout the day, trees have fallen onto cars, across roads and into power lines, causing pockets of homes to lose power.

“We want people to know not to park under or near the vicinity of a tree,” Safechuck said. Santa Barbara emergency officials have been bracing for worst-case scenarios, ordering the evacuations of about 630 homes that are tucked into fire-scarred canyons, near creeks, and at the base of the hills. Heavy rain can quickly saturate the terrain, just as it did in 2018 in Montecito — when precipitation fell quickly overnight and sent rivers of mud and boulders the size of houses hurtling down straight into neighborhoods, leveling many and ultimately killing 23 people. The body of a boy from that storm is still missing. That disaster was a glaring wake-up call for the coastal community, whose land is still not recovered from three significant wildfires, making it prone to mudslides.

As the rain thickened Sunday afternoon, the city stood mostly still. Coffee shops were largely empty, while hotels prepped rooms to potentially house employees who might not be able to get home if the risky floods that scientists are predicting due actually transpire.

A day after going door to door issuing evacuation orders, some members of Santa Barbara’s volunteer search and rescue team sat on white benches inside their command center, peering at maps of vulnerable communities and refreshing websites for updated predictions. It’s a tough waiting game, as weather models and predictions quickly change, said Bob Tench, an incident command leader who has lived in the area for about 30 years.

Santa Barbara’s SAR is a nonprofit made up of about 50 volunteers with day jobs such as teachers and engineers, who are now trained in swift water and other forms of rescue. With an event like this, Tench said, usually everyone drops what they are doing if they get a ping.

“As soon as it’s an evacuation like this, we get a full team response,” Tench said. “Because you just never know.”

The waterlogged system will encounter frigid air in the higher elevations. A general 3 to 6 feet of snow can be expected above 6,000 feet in the Sierra Nevada, where winds gusting up to 75 mph will combine with possible thundersnow and snowfall rates exceeding 3 inches per hour. Winter storm warnings are in effect and note virtually impossible travel. Snow will also fall in Nevada.

Impacts will wane late Monday in central and Northern California, but the state won’t finally shake the storm system until the latter half of Tuesday.

Where is the storm now?

On Sunday evening, a low-pressure system was located just offshore of north-central California, moving northeast. It was rapidly “deepening,” or intensifying, akin to a powerful atmospheric whirlpool spinning counterclockwise.

That spin was sweeping along a ribbon of robust tropical moisture all the way from Hawaii. The “atmospheric river,” or narrow band of extreme moisture, stretched more than 2,500 miles. Now the fire hose is hitting California, and won’t pinch off until Tuesday, at which point it will have swung down the entire coastline.

Timing

On Sunday evening, the atmospheric river was drenching large parts of California while dropping snow in the mountains. Most of the precipitation was falling from San Clemente northward; San Diego was still dry. The northern extent of the precipitation shield was just north of the Oregon border.

Overnight Sunday, models project rainfall to expand southward and eastward. Rain may ease or become more showery in the Bay Area while continuing to drench the zone from Santa Barbara to Los Angeles.

On Monday, the main atmospheric river will swing into Southern California, but intermittent downpours will continue across north-central and Northern California. That’s associated with the “cold core” of low pressure, or the low’s pocket of frigid air aloft, moving over the region.

A few additional thunderstorms may pivot ashore along the central coast of California as well. Isolated small hail can’t be ruled out.

Impacts

Flooding: From Santa Barbara and Los Angeles, a month or two’s worth of rain, or at least 4 inches, may fall; some models project the heaviest rainfall just east of Santa Barbara and just north of Los Angeles.

In the transverse ranges and Los Angeles County mountains, 8 to 15 inches of rain is possible. That will trigger major flood problems, particularly as the rain drains into the lower elevations. Rockslides and landslides are likely; recent heavy rains will bolster the risk of shallow landslides, since the top layers of soil are unstable, particularly on steeply sloped surfaces.

Winds: At the coast, gusts of 60 to 70 mph are possible between the Bay Area and Santa Barbara, with gusts over 70 mph possible along the coastal ranges. Inland, there could even be some gusts of 50 to 60 mph in the Sacramento Valley. Even San Diego is under a wind advisory, with gusts up to 40 mph possible.

Tornadoes: There is a low, but not zero, risk of an isolated spin-up tornado between San Jose and the Lompoc/Santa Maria area through Sunday evening.

Heavy snows: Several feet of snow is expected in the northern Sierra Nevada above 6,000 feet, with 2 to 6 feet above elevations of 7,000 feet. The snow is ongoing now, with snowfall rates probably exceeding 3 inches per hour. Thunder and lightning may sporadically accompany snowfall. Wind gusts of 75 mph or greater are possible on the Sierra Ridge. For the southern Sierra, expect 10 inches or more above 6,000 feet, with 1 to 2 feet above 7,500 feet.

Coastal flooding: Coastal flood advisories and/or high-surf advisories span much of the California coastline. Large breaking waves of 14 to 18 feet are expected just offshore. A storm surge of a couple of feet is also possible due to persistent onshore flow piling water against the coastline.

How long will this serious weather last?

The worst weather will pull south out of Northern California on Monday afternoon. By Tuesday, impacts will be waning in Southern California, and mostly over across the central and northern region.

Diana Leonard contributed to this report.

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