Pacific Northwest reeling from bomb cyclone; atmospheric river targets California

A bomb cyclone pounding Northern California and the Pacific Northwest with heavy rain and strong winds was already blamed for two deaths and will likely fuel flooding, rock slides, debris flows and power outages, the National Weather Service warned Thursday.

And more foul weather is on the way.

The first storm was forecast to linger into the weekend and produce an additional 6-12 inches of rainfall, the weather service said. An atmospheric river prompted a high-risk warning for excessive rainfall along the Northern California coast.

More than 260,000 homes and businesses were without power in Washington state and another 18,000 in California by 4 p.m. PT Thursday. Winds gusted as high as 85 mph in Oregon and more than a foot of rain fell in parts of Northern California, AccuWeather reported.

Dave Houk, senior meteorologist with AccuWeather, said areas already hit by several inches of rain will see more.

"It will rain hard for several hours, and that stream of heavy rain will be aimed right at Northern California before it starts easing on Friday," Houk told USA TODAY.

A developing storm system forecast to swing off the Oregon and Washington coastline on Friday will add to the region's weather woes, Houk said. But it should not rage quite like the first one, which drove wind gusts in excess of 70 mph across parts of the state, toppling trees and power lines. The coast may see 50-mph winds or more, but Seattle should be relatively safe with winds of 25-30 mph, Houk said.

Still, some additional power outages and damage are possible, he said.

"This one won't be as strong and won't strengthen as quickly," Houk said. "Hopefully it won't turn into what we have seen the last couple days.''

Winter weather risks: Winter could bring blizzards, nor'easters, bomb cyclones: What to know

Developments:

? More than 550 flights into and out of San Francisco International Airport had been canceled or delayed by 4 p.m. PT Thursday. The airport had over 500 cancellations and delays Tuesday.

? Up to 15 more inches of snow are possible for the Washington Cascades, which already were hit with more than a foot of snow. The storm could also bring several inches to western Montana, Idaho and northwestern Wyoming mountain ranges through early Sunday.

Bomb cyclone strikes: 2 dead, widespread power outages in Washington

Avalanche warnings, flood advisories in Northern California

Numerous roads were closed and vehicles on I-5 north of Redding were screened for snow chains Thursday morning as Northern California grappled with the impacts of the powerful storm. Redding, population 93,000, had received nearly 5 inches of rain since the storm began.

An avalanche warning was issued for Mt. Shasta in the southern Cascades and other parts of Siskiyou County, which are getting heavy snow that’s expected to be followed by rain.

In the coastal city of Eureka, the National Weather Service office said the Eel River as on track to reach "major flood stage'' at 25 feet by Friday. Wind gusts in the area could get up to 70 mph Thursday night.

Farther south, a big rig driving in the rain early Thursday jackknifed on the Bay Bridge connecting San Francisco to Oakland, blocking four of the five lanes and snarling traffic for hours. An all-clear was issued around 9 a.m.

Flash flood advisories will remain in place for Bay Area counties north of San Francisco until early Saturday, the weather service said. The Santa Rosa area in Sonoma County has received almost 7 inches of rain, leading to increasing reports of flooded roads.

Contributing: Redding Record Searchlight

Storm turns home into 'fixer-upper'

Nancy Dienes cringed when a tall Douglas Fir tree fell onto the roof of the Seattle home Dienes and her wife, Tracy Matthews, remodeled over the past several years. The couple did most of the work themselves.

"When we bought it, it was a fixer-upper,” Dienes told KOMO-TV. “And it kind of feels like a fixer-upper again. We already said we're going to rebuild.”

New York, New Jersey get respite from drought

The New Jersey Forest Fire Service lifted fire restrictions Thursday after the drought-ridden state finally received a good soaking overnight, easing concerns of wildfires spreading during an extremely dry fall. New Jersey recently went through its driest October on record and it stretched into November, leaving the entire state in severe or extreme drought conditions.

New York City also received its first substantial rainfall in seven weeks, a spell that had prompted officials to issue the city's first drought warning since 2002. One to three inches of rain are expected through Friday, allaying some concerns but falling short of pulling the area out of its own arid stretch.

"Not a drought buster, but it will help, especially with ongoing fire weather issues,'' the NWS office in New York City said.

Brush fires, most notably in Manhattan's Inwood Hill Park and Brooklyn's Prospect Park, have become a major problem this fall for the city's fire department, which said it responded to an unprecedented 271 of them in the first two weeks of November.

In addition, New Jersey and New York state crews have spent nearly two weeks battling the Jennings Creek Fire at the states' border, which has burned more than 5,300 acres. It is now mostly contained.

Two deaths reported in Washington

A woman was killed Tuesday when a tree fell on a homeless encampment in Lynnwood, north of Seattle, local officials said. A second woman was killed near Seattle when a tree fell on her home, Bellevue city officials said. Two people were injured when a tree fell on their trailer in Maple Valley, southeast of Seattle.

"Trees are coming down all over the city and falling onto homes," the Bellevue, Washington, Fire Department posted on social media as the storm raged. "If you can, go to the lowest floor and stay away from windows. Do not go outside if you can avoid it. Emergency responders are working hard to respond to weather incidents but are prioritizing life safety first."

What is a bomb cyclone?

A bomb cyclone – a potent cold-season coastal storm that's so-named because of its explosive strength – is colloquially known as a winter hurricane. Such storms undergo an intensification process known as bombogenesis, which is a quick drop in atmospheric pressure, marking the strengthening of the storm, according to the National Oceanic and Atmospheric Administration.

Bombogenesis is said to occur when a storm's central barometric pressure drops at least 24 millibars in 24 hours. A millibar is a way of measuring pressure. The lower the pressure, the more powerful the storm.

Some of the most intense winter storms to batter the country's coasts have been bomb cyclones.

The word "bombogenesis" is a combination of "cyclogenesis," which describes the formation of a cyclone or storm, and "bomb" for its explosiveness.

"This can happen when a cold air mass collides with a warm air mass, such as air over warm ocean waters," NOAA said. "The formation of this rapidly strengthening weather system is a process called bombogenesis, which creates what is known as a bomb cyclone."

What is an atmospheric river?

Sometimes called "rivers in the sky," atmospheric rivers are a major factor in extreme rain and snowfall in the West. They function much like rivers on the surface but can carry considerably more water than the Mississippi River.

This article originally appeared on USA TODAY: Bomb cyclone updates: Hundreds of thousands without power