‘Bomb cyclone’ threatens Northern California and Pacific Northwest

SEATTLE (AP) — Northern California and the Pacific Northwest are bracing for what is expected to be a powerful storm, with heavy rain and winds set to pummel the region and potentially cause power outages and flash floods.

The Weather Prediction Center issued excessive rainfall risks beginning Tuesday and lasting through Friday as the strongest atmospheric river — a large plume of moisture — that California and the Pacific Northwest have seen this season bears down on the region. The storm system is considered a “ bomb cyclone,” which occurs when a cyclone intensifies rapidly.

The areas that could see particularly severe rainfall as the atmospheric river stretching far over the Pacific Ocean heads toward land will likely reach from the south of Portland, Oregon, to the north of the San Francisco area, said Richard Bann, a meteorologist with the National Weather Service Weather Prediction Center.

“Be aware of the risk of flash flooding at lower elevations and winter storms at higher elevations. This is going to be an impactful event,” he said.

In northern California, flood and high wind watches went into effect Tuesday, with up to 8 inches (20 centimeters) of rain predicted for parts of the San Francisco Bay Area, North Coast, and Sacramento Valley.

A winter storm watch was issued for the northern Sierra Nevada above 3,500 feet (1,066 meters), where 15 inches (28 centimeters) of snow was possible over two days. Wind gusts could top 75 mph (120 kph) in mountain areas, forecasters said.

“Numerous flash floods, hazardous travel, power outages, and tree damage can be expected as the storm reaches max intensity” on Wednesday, the Weather Prediction Center warned.

In Northern California’s Yolo County, crews spent Monday clearing culverts, sewers, and drainage ditches to avoid clogs that could lead to street flooding. Mesena Pimentel said she hopes the efforts prevent a repeat of floods last February that inundated her property near Woodland.

“We had about ten inches of water in our garage, had a couple of gophers swimming around,” Pimentel told KCRA-TV. Woodland city officials set up two locations where residents could pick up free sandbags. Authorities urged people to stock up on food and charge phones and electronics in case power goes out and roads become unpassable.

Meanwhile, Southern California will see dry conditions this week amid gusty Santa Ana winds that could raise the risk of wildfires in areas where crews are still mopping up a major blaze that destroyed 240 structures. The Mountain Fire, which erupted on Nov. 6 in Ventura County northwest of Los Angeles, was about 98% contained Monday.

Winds will calm by the end of the week when rain is possible for the greater Los Angeles area.

In southwestern Oregon near the coast, 4 to 7 inches (10 to 18 centimeters) of rain is predicted — with as much as 10 inches (25 centimeters) possible in some areas — through late Thursday night and early Friday morning, Bann said,

A high wind warning has been issued for the north and central Oregon coast beginning at 4 p.m. Tuesday with south winds from 25 mph (40 kph) to 40 mph (64 kph), with gusts to 60 mph (97 kph) expected, according to the weather service in Portland. Gusts up to 70 mph (113 kph) are possible on beaches and headlands. Widespread power outages are expected with winds capable of bringing down trees and power lines, the weather service said. Travel is also expected to be difficult.

Washington could also see strong rainfall, but likely not as bad as Oregon and California. From Monday evening through Tuesday, some of its coastal ranges could get as much as 1.5 inches (3.8 centimeters) of rain, Bann said.

The weather service warned of high winds from Tuesday afternoon until early Wednesday for coastal parts of Pacific County, in southwest Washington. With gusts potentially topping 35 mph (46 kph) — and likely faster near beaches and headlands — trees and power lines are at risk of being knocked down, the Pacific County Emergency Management Agency warned.

Seattle Mayor Bruce Harrell warned residents Tuesday afternoon to prepare for strong winds, as the National Weather Service in the city predicts power outages and road closures due to downed trees and powerlines.

A blizzard warning was issued for the majority of the Cascades in Washington, including Mount Rainier National Park, starting Tuesday afternoon, with up to a foot of snow and wind gusts up to 60 mph (97 kph), according to the weather service in Seattle. Travel across passes could be difficult if not impossible.

Transportation officials in Washington told ferry riders to expect bumpy rides on Tuesday and said motion sickness medication might be helpful due to rough seas. Service on at least one route was temporarily halted by Tuesday afternoon because of stormy weather, Washington State Ferries said in social media posts.

Officials also urged motorists to consider delaying travel around the state until Wednesday because of high winds and heavy snow expected in the mountains.

“It will only be a winter wonderland in the sense that you’ll be wondering where the heck you are on any given patch of land,” the Washington State Department of Transportation said on social media.

Outside of the Pacific Northwest, the central and eastern Gulf Coast, including the Florida Panhandle, is at risk for flooding Tuesday, with 2 to 3 inches (5 to 7.6 centimeters) of rainfall are in the forecast. Low-lying and urban regions could see flash floods.

North Dakota’s first major winter storm of the season is forecast to lash the north-central part of the state with deteriorating conditions overnight into Wednesday, said National Weather Service meteorologist Zach Hargrove. Strong northwest winds from 20-30 mph (32.2-48.3 kph) with gusts up to 55 mph (88.5 mph) are expected to impede visibility, especially in open country where travel could be difficult, he said.

Bottineau and Rolette counties near the U.S.-Canada border could see 8-10 inches (20.3-25.4 cm) of snow, with up to 1 foot (0.3 meters) or higher closer to the border, Hargrove said. Lesser amounts of snow were forecast to the south. Bismarck could see 1-3 inches (2.5-7.6 cm) of snow, he said.

The storm is “definitely one to take seriously,” he said.