The Latest Atmospheric River to Bring Flooding, Landslides, Cascades Snow to Pacific Northwest

weather.com meteorologists
Published: February 1, 2020

A relentlessly persistent jet-stream pattern will deliver another round of heavy rain to the Pacific Northwest this weekend, with a threat of flooding, landslides and damaging winds.

A nearly west-to-east jet stream continues to span the North Pacific Ocean from Asia to western North America. When this pattern sets up, strong storms develop over the Pacific Ocean and are then guided by the jet stream toward some part of North America, from Alaska to California, depending on the jet stream's orientation.

Stormcast: How Much and How Long?

Heavy rain and high-mountain snow will continue this weekend in the Pacific Northwest, particularly in Washington state.

A landslide blocked all northbound lanes on Interstate 5 north of Seattle, near Bellingham, Saturday morning.

The soaking weather pattern triggered landslides earlier this week, affecting several state highways in Washington and western Oregon. A two-mile stretch of the Historic Columbia River Highway near Multnomah Falls, east of Portland, was closed after a small mudslide Tuesday.


Current Radar and Satellite

A deep plume of moisture called an atmospheric river will accompany this latest round of stormy weather Saturday. These pipelines of moisture sometimes span thousands of miles from Hawaii or the Western Pacific Ocean toward the West Coast.

This warmer system will wring out heavier rain where the atmospheric river makes landfall and will raise snow levels at which snow will fall to 6,000 to 7,000 feet in the Washington Cascades through early Saturday. Snow levels will fall sharply as the cold front swings through later Saturday.


Eastern Pacific Ocean Satellite, Moisture, Pressure Analysis

Through Sunday, parts of western Washington could pick up a few more inches of rain, particularly along western slopes of the Olympics and Cascades below snow level.

This could trigger flash flooding, river flooding and landslides, given saturated ground and rivers already running high.

The National Weather Service in Seattle said some rivers in western Washington may experience at least moderate flooding. A flood watch has been issued by the NWS for western Washington through Sunday morning.


Snow and Rain Forecast

Parts of the Cascades could receive another foot of snow. Travel might be impacted later Saturday into Sunday as colder air moves in and drops snow levels below passes.

Wind advisories have also been posted by the National Weather Service for much of western Washington north of downtown Seattle, as well as the Olympic Peninsula, through Saturday morning. Downed trees and power lines are possible in these areas.

The combination of strong winds and heavy, wet snow will likely lead to a high danger of avalanches in the Cascades, particularly in Washington.

There is a chance of the first dry day in awhile Monday before the next system, potentially with another atmospheric river, targets the Northwest beginning Tuesday. As a result, there could be more heavy rain and feet of Cascades snow next week.

(MORE: New Snowmaker to Spread From Northwest to Rockies, Plains and Midwest


Five-Day Forecast

November, December and January are typically the wettest months of the year in the Pacific Northwest. But the persistence of this stretch of wet weather since December is pushing toward record territory in some locations.

The second-longest period of consecutive days with measurable precipitation has been recorded near the coast of western Washington in Forks, where 46 straight days of precipitation has resulted in more than 36 inches of precipitation, as of Feb. 1. Records there have been kept for the past 54 years.

January also set a new record for the wettest all-time wettest month in Forks, according to NWS-Seattle, with 30.78 inches of rainfall. It rained here every day in January. They also smashed their record wettest January, picking up over a foot more precipitation than an average January.

Hoquiam, Washington, has seen only its third month with measurable precipitation each day, in records dating to 1953. The only other months this happened were January 1964 and February 1961.

Seattle averages 18 days each January with measurable precipitation – at least 0.01 inches. It had 28 such wet days in January 1953 and 2006.

The Weather Company’s primary journalistic mission is to report on breaking weather news, the environment and the importance of science to our lives. This story does not necessarily represent the position of our parent company, IBM.


The Weather Company’s primary journalistic mission is to report on breaking weather news, the environment and the importance of science to our lives. This story does not necessarily represent the position of our parent company, IBM.