A powerfulbomb cyclone” will combine with an atmospheric river to release more than a month of rain, hurricane-force wind gusts, and feet of snow into the mountains in parts of the Pacific Northwest and northern California.

A storm system off the Pacific Northwest is expected to rapidly intensify Tuesday in a phenomenon called “bombogenesis” and earning it the nickname “bomb cyclone.” It will intensify so much and so quickly that it could become a “triple bomb,” tripling the criteria needed to be considered a bomb cyclone, the National Weather Service in San Francisco said.

Bomb cyclones are formidable and discharge heavy snowfall and strong winds during the winter. This one could be among the most intense ever recorded for its location, a storm that only occurs “about once every ten years” and will generate “some of the strongest winds we’ve seen in several years” that will lift “very dangerous mountain winds”. seas 30 to 35 feet,” said the National Weather Service in Medford, Oregon.

This cyclone bomb will work with an atmospheric rivera long plume of water vapor moving like a river through the atmosphere, to wring heavy rain and snowfall into the mountains of the Pacific Northwest and northern California starting Tuesday. The pair will stop along the coast and hit the area with dangerous conditions throughout the week and weekend.

Parts of northwest California could see 16 inches of rain or more in 48 hours. More than a month of rain is expected in the northern San Francisco Bay area, mainly north of the Golden Gate Bridge, the weather service said. Rainfall of this magnitude is expected to cause significant urban flooding, debris flows on roads and river flooding.

Conditions will begin to intensify Tuesday afternoon. A Level 2 of 4 threat for flooding is in effect for parts of northwest California and southwest Oregon, where 2 to 5 inches of rain could fall, the Weather Prediction Center said .

The heaviest precipitation is expected to begin Wednesday and peak Thursday in northwest California. A Level 3 of 4 risk of flooding and precipitation is in effect there for Wednesday and a rare Level 4 of 4 high risk is in place for Thursday, according to the WPC.

It is difficult to overstate the importance of these high risks. They are issued less than 4% of days per year on average, but are responsible responsible for more than 80% of all flood damage and 40% of all flood deathsWPC search shows.

Three to six inches of rain could fall Wednesday and some areas could reach 8 inches. Thursday’s precipitation could meet or exceed Wednesday’s totals, especially in the high-risk area.

Heavy snowfall is expected in high altitude areas, where winter weather alerts are in place. Blizzard warnings are in effect for parts of the Washington Cascades, where snowfall of more than a foot and gusts of up to 60 mph are possible Tuesday afternoon through Wednesday morning.

“Traveling could be very difficult, if not impossible. High winds could cause significant damage to trees and power lines,” the National Weather Service office in Seattle warned.

One to four feet of snow is possible Tuesday through Wednesday in the Cascades and northern Sierra Nevada. Snowfall could create impossible travel conditions on Interstate 5 and Highways 31, 36, 66, 89, 97 and 140.

Strong winds will also intensify Tuesday and peak Tuesday evening in the region. They will be particularly strong offshore, and rare hurricane-force wind warnings have been issued for much of the coastal waters of the Pacific Northwest.

Widespread winds of 35 to 50 mph are possible inland with tropical storm force gusts up to 70 mph. Isolated gusts in higher elevation areas and across headlands and headlands could reach 85 mph, or hurricane force.

These powerful winds could cause potentially widespread power outages, damage to buildings and make travel difficult, especially for high-end vehicles.

Conditions will begin to improve by the weekend, but lighter rain could continue into next week.

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