Northern California and the Pacific Northwest are bracing for what is expected to be a powerful storm, with heavy rain and winds expected to batter the region and potentially cause power outages and flash flooding.

The Weather Prediction Center has issued a risk of excessive precipitation beginning Tuesday and continuing through Friday, as the most powerful atmospheric river – long plumes of moisture extending far over the Pacific Ocean – California and the Pacific Northwest have seen this season weigh on the region. The storm system intensified so quickly that it is considered a “bomb cyclone,” said Richard Bann, a meteorologist with the National Weather Service’s Weather Prediction Center.

Areas that could see particularly heavy precipitation as the large plume of moisture heads landward will likely extend from south of Portland, Oregon, to north of the San Francisco area, he said. he explained.

“Be aware of the risk of flash flooding at lower elevations and winter storms at higher elevations. That’s going to have a big impact,” he said.

In Northern California, flood and high wind watches go into effect Tuesday, with up to 8 inches of rain forecast for parts of the San Francisco Bay Area, the North Shore and the 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 reach 120 km/h in mountainous areas, forecasters said.

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

Will Southern California get rain?

Meanwhile, Southern California will experience dry conditions this week amid gusty Santa Ana winds, which could increase the risk of wildfires in areas where crews are still mopping up a fire major which destroyed 240 structures. THE Mountain Fire, which broke out on November 6 in Ventura Countywas about 98% contained Monday.

The winds will calm down by the end of the week, when rain is possible for the greater Los Angeles area.

In southwest Oregon near the coast, 4 to 7 inches (10 to 18 centimeters) of rain is forecast — with up to 10 inches (25 centimeters) possible in some areas — through Thursday evening and early Friday morning, Bann said:

A strong wind warning was issued for the northern and central Oregon coast starting at 4 p.m. Tuesday with southerly winds of 25 mph (40 km/h) to 40 mph (64 km/h), with Gusts up to 60 mph (97 km/h) expected, according to the Portland Weather Service. Gusts of up to 70 mph (113 km/h) are possible on beaches and headlands. Widespread power outages are expected due to winds capable of bringing down trees and power lines, the weather service said. Travel is also expected to be difficult.

Washington could also see heavy precipitation, but probably not as heavy as Oregon and California. From Monday night through Tuesday, some of its coastal ranges could receive up to 1.5 inches of rain, Bann said.

The weather service warned of high winds Tuesday afternoon through early Wednesday for coastal areas of Pacific County in southwest Washington. With gusts reaching 29 mph — and likely faster near beaches and headlands — trees and power lines are at risk of being toppled, the Pacific County Emergency Management Agency warned.

Washington State Patrol Trooper John Dattilo, a Tacoma-based patrol spokesman, posted on social media Monday afternoon that people should prepare for “some bad weather” Tuesday evening. “Stay off the roads if you can!” »

A blizzard warning was issued for the majority of the Cascades in Washington state, including Mount Rainier National Park, beginning Tuesday afternoon, with up to 12 inches of snow and wind gusts up to up to 60 mph (97 km/h), according to the Seattle Weather Service. . Crossing the passes could be difficult, if not impossible.

Outside of that region, the central and eastern Gulf Coast, including the Florida Panhandle, is at risk of flooding Tuesday, with 2 to 3 inches (5 to 7.6 centimeters) of precipitation expected, according to the weather service. Urban and low-lying areas may experience flash flooding.

Associated Press reporter Lisa Baumann contributed to this report.