The gloomy damp of Thursday morning will seem like fine weather by the end of the day, when the second in a series of three successive storms is expected to return heavy rainfall and gusty winds to the North Coast, forecasters said.
The heaviest rain will likely come overnight, but the Thursday evening commute will be plenty wet, National Weather Service meteorologist Diana Henderson said.
The storm is expected to drop 3-to-6 inches of rain on the area by Friday, she said.
"It's just going to be a blanket of gunk," Henderson said.
An even wetter storm was forecast for Saturday night, with total rainfall by Sunday exceeding a foot in the wettest locations - places like Cazadero, Venado and other coastal hill locations that typically receive heaviest rainfall, Henderson said.
But stream and creek flooding is possible as early as Friday morning because of saturated soils and the collection of runoff from Wednesday's drenching, the weather service said.
Flash flood warnings are expected, as well, the weather service said.
The Russian River is predicted to crest several feet shy of monitor stage in Guerneville and was not expected to present a flood risk, forecasters said.
That said, there remained the possibility of flash flooding even on the river, and forecasters urged residents to be aware and err on the side of caution.
Saturated soil and high winds, especially along the coast, were expected to contribute to the likelihood of falling trees and power poles, as well as mudslides.
"Keep an eye on the stuff around you - the trees and power lines and other stuff," Henderson said. "And slow down on the freeway, normal common sense stuff... People tend to kind of forget common sense stuff whenever there's weather."
A high surf advisory was to be in effect from 6 p.m. Thursday to 4 a.m. Friday, the National Weather Service said.
A representative at the U.S. Coast Guard's Bodega Bay Station said the surf already was rough Thursday morning, with heavy swells well above what was forecast.