A winter storm headed for the North Bay is already moving through counties to the north, downing trees and power lines and bringing moderate rainfall to the area, weather forecasters said.

The wind and rain that hits Sonoma County on Thursday afternoon will be just the start of what's expected to be mostly breezy, wet weather for 10 days — with one bright spot: Christmas Day, the National Weather Service said.

The wettest areas could receive more than 10 inches of rainfall by Dec. 30, meteorologist Mark Strobin said.

In the meantime, what Strobin called "some pretty good rain" over the next several days, as well as high winds — particularly Thursday afternoon into early Friday morning — were expected to bring down more trees and power lines, and make driving dicey for high-profile vehicles, the National Weather Service said.

A high wind advisory was to be in effect for the Marin and Sonoma coasts beginning at 1 p.m. through 4 a.m. Friday.

Gusts up to 45 or 50 mph "wouldn't be out of the realm of possibility," Strobin said.

Already, a Thursday morning power outage in the remote Sonoma County community of Annapolis darkened 185 homes and closed Horicon Elementary School for the day, PG&E and the Sonoma County Office of Education said.

A PG&E spokeswoman said crews had not yet determined what caused the 7:50 a.m. outage or when power might be restored.

But weather service personnel said falling trees and the like had already caused numerous outages in Mendocino and Humboldt counties.

More than half an inch of rain fell in Eureka between 6 a.m. and 9 a.m., with gusting winds, forecaster Bob Ruehl said.

"It's not as windy as it was earlier, but we did have wind gusts up to 52 mph earlier this morning," Ruehl said.

"It looks like it's working its way down to you," he said.