A powerful and dangerous storm lashed the Bay Area on Sunday, downing trees and utility lines, leaving tens of thousands of people with power and prompting evacuation orders in San Mateo and Santa Cruz counties amid the growing risk of flooding.
The “atmospheric river” storm drenched much of Northern California with 3 to 6 inches of rain as it swung in off the Pacific Ocean, bringing with it punishing gusts of wind that downed trees and left people throughout the Bay Area in the dark. Parts of the North Bay received even more rain — up to 10 inches in one spot.
Nearly 94,000 Pacific Gas & Electric customers were without power as of 1 p.m. Sunday, the utility provider said, with about half of those affected in Marin and Sonoma counties. About 25,000 of those customers were without power on the Peninsula, and 10,000 people didn’t have power in the East Bay.
Strong winds overturned a tractor-trailer and a semi on the Richmond-San Rafael bridge on Sunday afternoon, leaving two lanes closed, according to the California Highway Patrol. And in the Sierra, falling rocks closed a portion of Old Donner Road between Truckee and the summit.
The deluge prompted evacuations in communities hard hit by wildfires in recent years, with authorities warning of mudslides and debris flows that could easily sweep away people if not avoided.
Evacuations have been ordered in several areas across several coastal zones in San Mateo and Santa Cruz counties, largely in anticipation of heavier rains later on Sunday afternoon.
The areas include the Last Chance and Swanton road areas of Santa Cruz County, as well as properties near Año Nuevo State Park, Whitehouse Canyon Road and areas south of Gazos Creek Road east of Highway 1, along with Butano State Park and the community of Barranca Knolls, west of Cloverdale Road. The communities of Loma Mar and Dearborn Park also were included in the order, along with the community of Butano Canyon. (See map below.)
Authorities there urged people to be on guard for downed trees and the potential for mudslides.
An evacuation center was set up at Half Moon Bay High School, 1 Lewis Foster Drive in Half Moon Bay.
The storm — the strongest to hit the Bay Area in two years — is part of a massive atmospheric system that includes a river of moisture being pulled up from the tropics and a “bomb cyclone” hitting the Pacific Northwest with the power of a major hurricane, meteorologists said.
A cold front associated with the “bomb cyclone” — an area of rapidly decreasing pressure that was forecast to hit Oregon and Washington state — has swept across the region, bringing with it a “ribbon” of moisture from the Pacific Ocean.
“It’s almost like a plow, and it’s pushing up all this warm and moist air,” said Brayden Murdock, a meteorologist with the National Weather Service.
While the moisture was expected to put an end to the region’s fire season, it left wildfire-swept areas prone to mudslides and debris flows.
A handful of people showed up late Sunday morning at Half Moon Bay High School, which became an evacuation site amid the threat of flash flooding. Among those was Norm Armstrong, 64, whose house narrowly survived the CZU Lightning Complex fire in August 2020.
More than a year after evacuating for that blaze, he lamented having to once again flee — this time, due to the threat of flash flooding running off from that burn scar. He and his wife brought supplies to last two or three days.
“It is just a regular drill for us now,” Armstrong said.
Rainfall totals were highest in the North Bay. Mt. Tamalpais received 10.51 inches of rain from noon Saturday through noon Sunday, while 5 to 6 inches fell in Santa Rosa, according to National Weather Service rain gauges.
The heaviest rain was expected to hit San Francisco and the East Bay areas around noon Sunday, while the storm was forecast to reach the Santa Cruz mountains late Sunday afternoon.
Meanwhile, a 65 mph gust of wind was reported at Los Gatos at 8:32 a.m., and a 62-mph gust was recorded at Mt. Umunhum.
“The winds are stretching out pretty far ahead of this system,” Murdock said. “It’s going to be wind first, rain later.”
Mt. Tamalpais was forecast to receive 12 to 13 inches of rain from late Saturday through Monday morning, Murdock said. San Francisco could see 7 inches, and the East Bay hills 5 inches. Most of Santa Clara County is forecast to receive 1.5 to 2 inches, and the Santa Cruz Mountains could get 7 inches of rain.
“It’s a marathon,” Murdock said. “It will be a long few hours, with such heavy rain coming through.”
Check back for updates as this story develops.
The map below shows the evacuation zones.