Northern California faces possible record-breaking rainfall from atmospheric river and another storm is coming

By Karina Tsui, Robert Shackelford and Mary Gilbert, CNN

(CNN) — A powerful atmospheric river is unleashing torrential, flooding rainfall across Northern California and parts of the Pacific Northwest in the wake of a historically strong bomb cyclone — and another storm is on the way.

A rare level 4 of 4 high risk of flooding rainfall is in effect Thursday as the atmospheric river — still boosted by the diminishing bomb cyclone — points a firehose of moisture at the coast, according to the Weather Prediction Center.

“Life-threatening flooding across coastal areas of northwest California is expected due to the very strong and long duration atmospheric river currently impacting the region,” the center warned Thursday. “Dangerous flooding and debris flows are likely which will include rock and landslide activity.”

Widespread rainfall of 3 to 6 inches with isolated totals of more than 10 inches are possible across the region on Thursday alone. Combined with rainfall from Wednesday, a potentially record-breaking 16 inches or more of rainfall is possible through Thursday, especially in Northern California.

More than a foot of rain has already fallen in part of the Coastal Range – just north of the San Francisco Bay Area – from Tuesday morning to Thursday morning, according to NOAA data.

Mountain snowfall also buried parts of Northern California and Oregon Cascades. More than a foot of snow fell in parts of the Cascade Mountains and in California by Thursday morning. More snow is on the way for Northern California Friday and through the weekend.

Flooding forced road closures Thursday in Northern California’s Sonoma County, including its largest city, Santa Rosa, some 55 miles north of San Francisco, social media posts from state and local authorities show. Roads flooded in multiple locations, the fire department said Thursday evening, urging residents to “avoid unnecessary travel during this time.”

Approximately 150 people had to shelter in place Thursday at a medical center and a hotel in Santa Rosa because of flooding outside, but the water was receding and the fire department was working on getting them out, the department’s Paul Lowenthal said.

About a dozen small landslides also struck across Northern California in a 24-hour period, including one on Highway 281 Wednesday morning that caused a vehicle crash, according to the Associated Press.

The storm’s rain and snow were creating “slick roads and poor visibility” that could make driving treacherous, Cal Fire said Wednesday in a post on X.

“Remember to slow down and drive cautiously in these hazardous conditions,” Cal Fire said. “Ensure your windshield wiper blades are in good condition, use your headlights for better visibility, and increase the distance between your vehicle and others on the road.”

As the deadly bomb cyclone helping to fuel the atmospheric river moves away from the coast Thursday, the National Weather Service is monitoring another storm that has the potential to strengthen on the heels of the first one.

This new storm is expected to move toward the Northwest coast Friday and strengthen. The likelihood of it strengthening enough to become another bomb cyclone is diminishing. Though it will be less intense, it will still usher in another round of gusty winds, rain and snow.

It will bring gusty winds back to Washington, where hundreds of thousands remain without power after being battered by the historic bomb cyclone’s hurricane-force winds earlier this week.

“We are prepared to respond if there is new damage to the system,” a release from Puget Sound Energy said Thursday.

More than 240,000 customers in Washington are still without power as of Thursday night – down from its peak of more than half a million customers.

Customers in Pierce County and Thurston County could have power restored by Thursday night but those in Whatcom, Skagit, Island and Kitsap counties may need to wait until Friday evening, and the majority of customers in King County, where Seattle is located, should expect to be without power until Saturday, according to the provider.

Some of the worst bomb cyclone damage occurred in King County, the Puget Sound Energy said.

“The high winds and resulting tree damage not only downed the smaller, local power lines, but also damaged the larger transmission lines – the larger lines that bring power into communities,” PSE said in a post on X.

Some utility crews have also been struggling to restore power due to limited access to hard-hit areas because of blocked roads and mudslides. Power restoration crews from other states and Canada were helping with the efforts, the power provider said Thursday.

A deadly, historic bomb cyclone

Although the first storm never made landfall, historic bomb cyclones can still bring devastating effects.

At least two people were killed in Washington state from strong winds that felled trees. One, a woman in her 50s in Lynnwood, north of Seattle, and another – killed while showering in her King County home, according to the Bellevue Fire Department.

Video shows extensive damage to trees, powerlines and homes across the state, where police and fire workers have been working to remove tree debris scattered across roads, on top of cars and a leaking propane tank.

Southeast of Seattle, two people in Maple Valley were rescued and taken to a nearby hospital after a tree fell on their trailer. While one person was freed quickly, it took firefighters an hour to extricate the second, according to Puget Sound Fire.

The storm was “one of the worst windstorms we’ve had in recent memory,” Issaquah Mayor Mary Lou Pauly said Wednesday. “We are seeing significant damage from trees (and) most of our traffic signals are out.”

A tree slammed into Washington resident Rob Corcoran’s home Tuesday evening and when it did, he told CNN it sounded like a jet landing on his roof.

“I didn’t even go outside because I was scared, I could be hit with flying debris,” Corcoran said. “I had no idea it was as bad as it is.”

An Amtrak train en route from Vancouver collided with a fallen tree on tracks north of Seattle Tuesday night, according to a statement from Amtrak. No injuries were reported among the 48 passengers on board and they were able to complete their journeys via alternate transportation. One engineer was hospitalized for evaluation and later released, according to Amtrak.

CNN’s Rebekah Riess, Isaac Yee, Hanna Park, Sara Smart, Andy Rose, Mike Madrigal and Taylor Romine contributed to this report.

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