The second in a series of storms slammed Northern California on Friday as heavy rain and strong winds knocked out power, tied up traffic and caused flooding along some stretches.

The weather also may be behind the death of a Pacific Gas & Electric worker in West Sacramento who was killed after his truck crashed into a traffic signal pole during the stormy weather.

 In the city's affluent Pacific Heights neighborhood, traffic was blocked for hours after a large tree crashed down, smashing a car and obstructing a busy street.

As of 7 p.m., 110 flights were cancelled or delayed at the San Francisco International Airport, 20 of those were added late Friday afternoon as the rain and wind pick up.

A flash flood watch will remain in effect for most of the San Francisco Bay Area extending to the Santa Cruz Mountains throughout the weekend. A constant barrage of downpours could lead to standing water and overflowing drains, said Diana Henderson, a forecaster with the National Weather Service in Monterey.

Part of the Highway 9 in Santa Cruz County was shut down in both directions, due to downed power lines. Officials said the closed section of Highway 9 may not reopen until  7 a.m. Saturday.

The North Bay was seemingly hit the hardest, as parts of Sonoma County received more than 7 inches of rain and areas in Napa County received nearly 6 inches, Henderson said.

"It's not a super storm by any measure, but this is pretty significant," Henderson said. "We should see periods of moderate to heavy rains."

With rain expected all weekend long, Tony Negro, a contractor from Penngrove, in Sonoma County, said he is worried about water flooding his workshop.

"I'm on my way to get some sand bags," he said.

Thousands of people were without power in that area after an outage that also affected the San Francisco-Oakland Bay Bridge. The suspension span of the bridge was briefly in the dark as traffic was backed up longer than usual because of rain and strong wind gusts.

Also, a mudslide shut down a stretch of Highway 84 east of Fremont, the California Highway Patrol reported. There was no estimate on when it would reopen.

In Sacramento, an empty big-rig jackknifed in the southbound lanes and struck the median divider on Interstate 5 south of downtown Friday morning, the CHP said.

"I would definitely say it's weather-related. The reports came in that he hit a water puddle and hydroplaned and couldn't correct," CHP Officer Mike Bradley said. "A lot of high-profile vehicles, especially the lighter ones, are getting windblown and having some problems maintaining their lane."

No one was injured in the crash on I-5, California's main north-south highway. But a second vehicle also was damaged and had to be towed, while workers cleaned up diesel fuel spilled from the tractor-trailer.

In West Sacramento, police say wet conditions may have been a factor when a PG&E worker died after he lost control of his vehicle and slammed into a traffic pole. PG&E workers at the scene told KCRA-TV that the driver had been working overtime and was returning from Clarksburg in southern Sacramento County.

The weather also caused power outages throughout the region.

About 2,800 PG&E customers in the Bay Area are still without power Friday evening because of storm-related outages, a utility spokesman said.

The affected customers include 2,200 in the North Bay, 550 along the Peninsula, 300 in the East Bay, 140 in the South Bay and 50 in San Francisco, PG&E spokesman Fiona Chan said.

An additional 570 customers are without power in the Santa Cruz Mountains as well as just over 740 others in Santa Cruz and Monterey counties, Chan said.

The storm had caused outages to nearly 16,000 Bay Area PG&E customers at its peak overnight, according to PG&E.

Henderson said rain in the region is expected to taper Saturday, but return later that night into Sunday. The storms could create the possibility of rock and mud slides in areas already saturated and affected by wildfires this summer.

In Los Angeles, conditions were wet and gloomy as downtown skyscrapers disappeared in low-hanging clouds.

Elsewhere in the West, a state of emergency was declared in Reno, Sparks and Washoe County in Nevada due to expected flooding as a storm packing heavy rain and strong winds swept through the area. Reno city spokeswoman Michele Anderson said public servants would be working overtime through the weekend to control what's expected to be the worst flooding there since 2005. The National Weather Service issued a flood warning along the Truckee River.

The weather also prompted cancellations of Christmas parades and tree lightings in Sparks and Truckee, just across the border from California.

Also, a storm rushed through southern Oregon this week, lingering inland over the Rogue Valley and dropping record rainfall. It largely spared coastal Curry County and its southernmost city, Brookings, which were still recovering from a storm this month.

"We are still vigilant for landslides and road closures and trees down, but so far -- knock on wood -- we are still good to go," Curry County Sheriff John Bishop said.

Forecasters said the region should expect more storms over the next few days.