Bay Area Braces for Quadruple Threat: Rain, Wind, Surf and King Tides

The Bay Area is bracing for a quadfecta of environmental conditions this week — heavy rain, strong winds, high surf and king tides — that will create blustery conditions and potential flooding across the region.

“It’s like everything all at once,” said Nicole Sarment, a meteorologist with the National Weather Service’s Bay Area office.

After Wednesday night brought moderate rain, Sarment said the Bay Area will get a short reprieve before a larger, windy, wet storm settles over the region late Friday through Saturday.

Sarment foresees flooding due to heavy rain, high surf and king tides. Starting Friday, according to the weather service’s online forecast discussion, “there are going to be poor conditions everywhere, especially on the water or at the beach.”

“The storm door is now opening up for us,” said Rick Canepa, a meteorologist with the weather service’s Bay Area office. “We’re still in the early stages of the winter season. So it’s a bit of a tough call, but there’s plenty of potential ahead of us.”

Lowland parts of the region will likely receive about an inch of rain during the 24-hour storm, but the North Bay is of top concern because up to 5 inches of rain could fall at the highest elevations, Sarment said.

“The North Bay just got hammered with an atmospheric river a few weeks ago, so their soils are a lot more saturated,” she said.

Saturated soil is unable to absorb as much rainwater, leading to more runoff during a heavy storm and raising the flood risk for rivers, streams and roadways.

A flood watch is in effect from 2 p.m. Friday through Saturday afternoon for the North Bay. Three Sonoma County waterways could flood: Laguna de Santa Rosa, the Russian River and Mark West Creek.

“If a thunderstorm or really heavy showers were to develop, that poses a risk for flooding,” Sarment said.

King tides — caused by a stronger than normal gravitational pull when the sun, moon and Earth align — could push water up the coast and bayshore with high-tide levels between 5 and 12 feet through Monday. On top of the higher tides, the weather service has issued a high surf advisory from 1 p.m. Thursday through 4 p.m. Saturday with large breaking waves on the order of 18 to 22 feet.

“Because the tide overall is going to be higher, those bigger waves will be able to run up the beach farther,” Sarment said. “Overall, it’s not going to be a good weekend to go out and about.”

The higher tides increase flooding risk in places like San Francisco’s Embarcadero and the Mill Valley–Sausalito Bike Path in Marin County. The highest tides could reach nearly 12 feet on Saturday north of San José’s bayshore community of Alviso, according to the California King Tides Project.

The California Coastal Commission asks the public to submit photos of waves and rising groundwater during this weekend’s king tides. The images will be used by climate scientists and government officials “to validate sea level rise models and assess local vulnerabilities to erosion and flooding,” the commission wrote in a press release.

Conditions will improve on Sunday before a third round of rain moves through the Bay Area on Monday, but Sarment said impacts from next week’s system look minor so far.

There is some good news for the not-so-distant future: After next week’s storm, she said, the region will “have better weather” just in time for the Christmas holiday.