‘Good portion’ of Bay Area to see rain thanks to early season storm

A cold front west of San Francisco is bringing wet weather to the region on Thursday, with the North Bay expected to get the most precipitation.

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While the average rainfall for Santa Rosa in September is 0.15 inch, the National Weather Service predicts it could receive more than that amount in a single day, with about 0.25 inch of rain expected Thursday. The Santa Rosa Airport has already received 0.17 inch of rain in the past 48 hours, according to National Weather Service meteorologist Roger Gass.

While a historically strong El Niño is expected to potentially bring wet weather to California this winter, this rain is not linked to that weather phenomenon, Gass told SFGATE.

“We actually have a strong low pressure off of the Pacific Northwest coast that’s dragging a frontal boundary across our region today and into tomorrow,” he said. That low-pressure system is bringing cooler temperatures and showers.

The weather pattern has already brought significant rain to coastal ranges, with Mount Tamalpais getting 0.64 inch in the past 48 hours. The area is expected to get about another half an inch on Thursday. 

While the wet weather was mainly confined to the North Bay earlier this week, the showers are likely to head further south Thursday, with the front expected to cross the Golden Gate around midday, Gass said. The incoming weather pattern could mean showers on and off in San Francisco and areas further south until the late afternoon.

“While a good portion of the Bay Area should see some rain, it likely won’t be more than a few hundredths outside of the coastal mountains,”the weather service said in its forecast discussion.

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The weather is expected to dry out by the evening commute, and temperatures should start to warm Friday and through the holiday weekend.

Gass said two hurricanes currently churning in the Pacific Ocean could affect the Bay Area this weekend, but not via precipitation. Instead, the strong storms could cause beach hazards thanks to strong swells.

“We are expecting an increased risk of sneaker waves and strong rip currents and breaking waves up to 10 feet, especially along the south and southwest facing beaches,” Gass told SFGATE. 

The weather service warned that waves from these storms can travel over 1,000 miles, causing dangerous beach conditions. 

“Avoid the water if you’re not an expert swimmer,” the weather service said in the forecast discussion.