A new storm is gathering strength off the Northwest coast, threatening to bring further damage to areas already reeling from a historically strong bomb cyclone. The storm is adding energy to an atmospheric river that has already dumped nearly a foot and a half of rain on parts of California this week.

In Washington, gusty winds from the new storm are expected to increase throughout the day, with more than 180,000 homes and businesses remaining without power for the third day early Friday morning, according to PowerOutage.us. The earlier bomb cyclone brought hurricane-force winds that battered parts of the state, knocking out power to more than half a million customers and killing at least two people in Washington state.

The new storm is expected to bring wind gusts up to 30 mph through the Seattle area Friday afternoon, with gusts up to 60 mph possible along Washington’s coast. These winds aren’t as strong as those generated by the earlier bomb cyclone, but the soaked soil makes trees more unstable and susceptible to being felled by gusty winds.

Meanwhile, a potent atmospheric river is directing a deluge of moisture at Northern California. A level three of four risk of flooding rainfall is in effect Friday for parts of the northern Sierra Nevada and the Coastal Range, just north of the San Francisco Bay Area, according to the Weather Prediction Center. Nearly 18 inches of rain has fallen in parts of Northern California since Tuesday, and an additional 5 to 10 inches of rain is possible into Saturday morning.

"Life-threatening flooding is likely across portions of northern California, where additional amounts of 3-5" are expected, mainly over coastal areas. As much as 4-10" of rain are possible for the northern Sierra Nevada. Dangerous flooding, rock slides, and debris flows remain likely today," the Weather Prediction Center said.

Flooding has already forced road closures in Northern California’s Sonoma County, including its largest city, Santa Rosa. Approximately 150 people had to shelter in place at a medical center and a hotel in Santa Rosa because of flooding outside. About a dozen small landslides also struck Northern California in a 24-hour period earlier this week.

Heavy mountain snow in Northern California is also expected to pick up again Friday and continue into early next week. An additional one to four feet of snow is expected by Tuesday.

Joel Malkin