Atmospheric river could cause landslides, flooding in North Bay

Shallow landslides and flooding could occur this weekend as up to 8 inches of rain pour into the North Bay during what the National Weather Service is calling a “weak atmospheric river.”

Two rounds of rain, from Friday to Monday, could dump about 2 to 6 inches of rain across area valleys while coastal ranges in northwest Sonoma County, like those north of Jenner, could see up to 8 inches, said Sarah McCorkle, a meteorologist with the weather service’s Monterey office.

Though not as powerful as those that drenched the North Bay last winter, the expected atmospheric river will be one of the bigger storms so far this winter.

Still, it is a normal system for the time of year, McCorkle said, and should bring mostly beneficial rain to the region.

“It is one of the more impactful storms we have seen so far this winter just as far as expected rainfall amounts,” she said. “In addition to that, with the soils being saturated, an increased chance for landslides.”

North Bay rain totals are about an inch below normal totals for the year and about 1.4 inches below normal since the beginning of the water year, Oct. 1.

The first round of rain, beginning Friday morning and into Saturday night, could bring about 1 to 3 inches of rain to the area. Another 1 1/2 to 4 inches is expected from Sunday morning into Monday, when there’s also a 20% to 30% chance for thunderstorms.

Chances for landslides and flooding ― quickly rising creeks and streams, and standing water on roads ― will increase from early Sunday to Monday morning.

Officials predict the Russian River will begin rising Saturday and could reach up to about 16 1/2 feet ― about 1 1/2 feet above flood level ― at Hopland in Mendocino County on Monday morning, according to the California Nevada River Forecast Center.

The river crested above flood level Sunday at the same location.

The river observation site in Guerneville could reach up to 25 1/2 feet Monday night, below the 29-foot level prompting initial action.

Residents should mostly be weary of the saturated soils. “If you live close to a hillside, just be extra vigilant,” McCorkle said.

You can reach Staff Writer Madison Smalstig at madison.smalstig@pressdemocrat.com. On X (Twitter) @madi.smals.