(Adds storm originating from hurricane-force low-pressure system)
By Sharon Bernstein and Steve Gorman
SACRAMENTO, Calif., Jan 4 (Reuters) - Emergency crews braced for the latest bout of high winds and torrential rains sweeping California on Wednesday, renewing the threat of power outages and deadly flooding that gripped parts of San Francisco Bay and Sacramento over New Year's weekend.
The "atmospheric river" - an airborne current of dense moisture flowing from the ocean - was expected to drench much of California ahead of a storm front bringing additional showers to low-lying areas and more snow to the Sierra Nevada Mountains through Thursday.
The incoming blast of extreme winter weather - the next in a succession of storms expected to wash over California in the coming weeks - originated from a sprawling, hurricane-force low pressure system churning over the eastern Pacific, forecasters said.
The National Weather Service (NWS) predicted widespread rainfall totals of 3 to 6 inches, with up to 3 feet of fresh snow in Sierras.
Authorities warned the heavy downpours would likely unleash flash flooding and mudslides, especially in areas where the ground remains saturated from rains that soaked northern California days earlier. Fire-ravaged hill slopes are also particularly vulnerable to slides.
High-wind warnings were posted along the central California coast north through the Bay area and into extreme northern California and Oregon. The National Weather Service (NWS) said gale-force gusts were expected to uproot trees, shear off limbs and knock down power lines, disrupting electricity service in many areas.
San Francisco's transit agency halted its famed cable car service through Thursday due to inclement weather, and scores of commercial flights were canceled at San Francisco International Airport.
Stormy weather was blamed for at least one traffic death in the north Bay city of Fairfield, where pooled water on a roadway sent a car crashing into a utility pole, killing the driver, the San Francisco Chronicle reported.
Voluntary evacuation notices were issued for homes along three roads in a flood-prone area of Alameda County, across the bay from San Francisco, citing threats posed by "the impending storms, saturated soils and current runoff."
EMERGENCY FOOTING
Governor Gavin Newsom declared a state of emergency on Wednesday to support the state's winter weather hazards response, and activated California's flood operations center.
The governor's Office of Emergency Services said it had staged crews in several northern counties likely to be hardest hit by flooding, and where previous wildfires have stripped hillsides of vegetation, leaving them at high risk of mudslides.