Atmospheric river bringing rain, cold front to Sonoma County

Rain, cold temperatures and a possible thunderstorm are all on deck as another atmospheric river builds offshore before moving through the North Bay starting Sunday.

The new system is expected to move through the region quickly and deliver less rain than the powerful atmospheric river in October, said Brian Garcia, a meteorologist with the National Weather Service. That storm dumped up to a foot of rain in some areas of county, setting a new 24-hour record in Santa Rosa, where 7.83 inches fell in one day.

The incoming weather system is expected to arrive Sunday, and skies are forecast to clear up Tuesday.

Sonoma County’s coastal areas, including The Sea Ranch, will likely experience the opening action late Saturday.

“That cold front will sweep across the county through the Bay Area (Sunday) and bring a little bit of rain,” Garcia said.

The coastal hills and northern end of the Mayacamas range ― areas including St. Helena and The Geysers ― are expected to see the most rainfall, with totals topping about 5 inches, Garcia said. Areas along Highway 101 will likely see rainfall totals reach 2 to 3 inches.

Rainfall is projected to diminish Sunday into Monday, Garcia said, and there is a slight chance of a thunderstorm and small hail on Monday.

“Typically we would see thunderstorms and small hail come through in the spring, but it’s not abnormal to see it (now),” said Garcia.

Along the lower Russian River, the Monte Rio Fire Protection District is fueling up chainsaws and distributing sandbags to a few problem areas, said Monte Rio Fire Chief Steve Baxman.

The preparations are typical of how the district prepares for any big storm, Baxman said.

“Usually with a storm like this we get a lot of trees down,” Baxman said.

As with the freezing overnight lows that preceded the storm Friday into Saturday, a second bout of cold temperatures will follow when the rain exits the area on Monday.

“By Tuesday morning, we’ll start to see the mercury plummet,“ Garcia said. ”We’ll get cold temperatures rolling in.“

Snow may also crop up at the higher elevations around 2,000 and 3,000 feet in the Mayacamas Mountains.

In the Lake Tahoe basin, snowfall is forecast to eclipse five feet over a four-day period, Garcia said.

“This is great for the snow pack, for the drought situation,” Garcia said. “Everything is welcome.”

You can reach Staff Writer Emma Murphy at 707-521-5228 or emma.murphy@pressdemocrat.com. On Twitter @MurphReports.