SEATTLE– Northern California and the Pacific Northwest are preparing for what is expected to be the strongest storm of the season yet, bringing heavy rain and winds to lash the region and possibly cause power outages and flash flooding.

The Weather Prediction Center has announced risks of excessive rainfall beginning Tuesday and continuing through Friday as the strongest atmospheric river (long plumes of moisture that extend far across the Pacific Ocean) hitting California and the Pacific Northwest this season has had a negative impact on the region. The storm system has intensified so quickly that it is being considered a “bomb cyclone,” explained Richard Bann, a meteorologist with the National Weather Service Weather Prediction Center.

The areas that could see particularly heavy rainfall as the large plume of water moves toward land will likely extend from south of Portland, Oregon, to northern San Francisco, he explained.

“Consider the risk of flash flooding at lower elevations and winter storms at higher elevations. This will be an impactful event,” he says.

Flood and high wind warnings go into effect in Northern California on Tuesday, with up to 8 inches of rain forecast for parts of the San Francisco Bay Area, the North Coast and the Sacramento Valley.

A winter storm watch was issued for the northern Sierra Nevada above 1,066 meters (3,500 feet), where 28 cm (15 in) of snow was possible over two days. Wind gusts could reach up to 120 kilometers per hour in mountain areas, forecasters say.

“Numerous flash flooding, hazardous travel, power outages and tree damage can be expected as the storm reaches maximum intensity,” the National Weather Service Weather Prediction Center warned Wednesday.

Meanwhile, Southern California will experience dry conditions this week amid gusty Santa Ana winds that could increase the risk of wildfires in areas where crews are still working to clear a major blaze that has destroyed 240 structures. The Mountain Fire, which broke out on November 6 in Ventura County, northwest of Los Angeles, was about 98% contained on Monday.

Winds will decrease toward the end of the week when rain is possible in the greater LA area.

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

A high wind warning was issued for the coast of northern and central Oregon at 4 p.m. Tuesday, with southerly winds of 25 mph (40 km per hour) to 40 mph (64 km per hour), with gusts up to 60 mph (97 km per hour) expected, according to the National Weather Service in Portland. Wind gusts of up to 113 km per hour are possible on beaches and headlands. Widespread power outages are expected, with winds likely to down trees and power lines, the weather service said. Travel is also expected to be difficult.

Washington could also see heavy rainfall, but probably not as bad as Oregon and California. As much as an inch and a half of rain could fall in some coastal areas Monday evening through Tuesday, Bann said.

The National Weather Service warned of high winds in coastal areas of Pacific County, southwestern Washington, from Tuesday afternoon through early Wednesday. With wind gusts potentially exceeding 35 miles per hour – 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 patrol spokesman based in Tacoma, posted on social media Monday afternoon that people should be prepared for “some bad weather” Tuesday evening. “Stay off the road if you can!”

A blizzard warning was issued as of Tuesday afternoon for most of Washington’s Cascades, including Mount Rainier National Park, with up to a foot of snow and wind gusts up to 60 mph (97 kph), according to the National Weather Service in Seattle. Traveling over passes can be difficult, if not impossible.

Outside of this region, the central and eastern Gulf Coast, including the Florida Panhandle, is at risk of flooding on Tuesday, with 2 to 3 inches (5 to 7.6 centimeters) of rainfall, according to the National Weather Service. Low-lying and urban areas may experience flash flooding.

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Associated Press reporter Lisa Baumann contributed to this report.