Atmospheric River Soaks Bay Area: See Rain Totals

SAN FRANCISCO, CA — An atmospheric river storm continued to drench the Bay Area on Monday, creating dangerous driving conditions and bringing powerful winds to parts of the region.

The multiday storm was also forecast dump more than 8 feet of snow on the highest peaks in Northern California.

A flood advisory expired for the San Francisco Bay Shoreline just after noon, but rainfall reportedly flooded highways and local roads throughout the morning, National Weather Service officials tweeted.

📡Radar Update 12:35 PM - Rain continues to fall across the #BayArea. Some of the rain will be heavy at times. Please heed any current road closure, water covering roads, or debris on road. Turn around, don't drown. #cawx #AtmosphericRiver pic.twitter.com/HAl0gwtYX7
— NWS Bay Area (@NWSBayArea) December 13, 2021

"The bulk of rain is going to occur midnight Monday morning and through the day," Jan Null, who runs the private forecasting service Golden Gate Weather Services, told San Francisco Gate. "This is going to be a good 18 hours of relatively solid rain."

By noon, San Francisco received more than 2 inches of rain from the powerful storm.

The National Weather Service released the following 48-hour rainfall totals for the Bay Area around 5 a.m.

• Mount Tamalpais: 8.74 inches
• Woodacre: 5.35 inches
• Ben Lomond Mountain: 4.78 inches
• Cazadero: 3.17 inches-St.
• Helena: 2.56 inches-
• Mount Umunhum: 2.33 inches
• Oakland: 1.39
• Oakland Hills: 1.56 inches
• San Francisco Airport: 1.47 inches
• Napa: 1.39 inches
• San Francisco: 1.35 inches
• Livermore: 0.20 inch
• Altamont: 0.09
• San Jose: 0.08 inch

As of 11 a.m. the fastest winds were recorded in the Santa Cruz mountains, with gusts topping 79 mph, followed up by 77 mph winds in Alameda County, south of Livermore, NWS officials said.

Peak wind gusts with the storm today, topped by 79mph in the Santa Cruz Mtns and followed up by 77 mph in Alameda county south of Livermore.

Gusty winds continue through the day.#cawx pic.twitter.com/5InKcJDTVs
— NWS Bay Area (@NWSBayArea) December 13, 2021

“This is a pretty widespread event,” said National Weather Service meteorologist Anna Wanless in Sacramento. “Most of California, if not all, will see some sort of rain and snow.”

Residents caught a break from the rain midday, but precipitation was expected to return.

"While a few areas are starting to see some sun and breaks in the rain, more rain is possible this afternoon and evening," weather officials tweeted.

As the rain let up in San Francisco, police were working with Caltrans to clear freeway drains and prepare roadways for next downpour.

With a slight break in this current storm, your CHP San Francisco officers are currently working with Caltrans to ensure the freeway drains are clear for the next downpour of rain anticipated for later this afternoon/evening. Please drive at a safe speed for weather conditions! pic.twitter.com/ZzBAOJqbNX
— CHP San Francisco (@CHPSanFrancisco) December 13, 2021

Aside from roadways flooding, streams and creeks were rising rapidly around the Bay Area on Monday morning as the atmospheric river continued to soak the region.

Drivers on some mountainous passes over the weekend had to put chains on their tires and were warned of possible road closures this week.

Authorities urged Californians to delay travel and stay indoors in some areas of Northern California. The rain could cause minor flooding and rockslides, especially in areas that have been scarred by wildfires, forecasters said.

South of the San Francisco Bay Area, a 40-mile stretch of Highway 1 in California's Big Sur area was shuttered as a precaution until Tuesday. The scenic coastal route frequently takes damage during wet and blustery weather.

Nearby Monterey County residents who live close to burn scars from last year's Dolan Fire were warned to be prepared to evacuate if rains loosen hillsides and cause debris flows.

The Bay Area has not seen widespread rain since October's atmospheric river or "bomb cyclone" storm, which brought historic rainfall, toppled trees, flooded busy highways and homes, prompted evacuations and cut power to about 380,000 people.

The storm was expected to bring much needed moisture to the broader region that’s been gripped by drought caused by climate change. The latest U.S. drought monitor shows parts of Montana, Oregon, California, Nevada and Utah are classified as being in exceptional drought, which is the worst category.

Most western U.S. reservoirs that deliver water to states, cities, tribes, farmers and utilities rely on melted snow in the springtime.

The atmospheric river storm this week is typical for this time of the year but its especially notable because it’s the first big snow that is expected to significantly affect travel with ice and snow coating the roads, strong wind and limited visibility, according to Wanless.

Atmospheric rivers are "relatively long, narrow regions in the atmosphere — like rivers in the sky," according to the National Oceanic and Atmospheric Administration. A bomb cyclone occurs when a storm undergoes bombogenesis, meaning it rapidly intensifies over a 24-hour period, according to NOAA.

The Associated Press contributed to this report.