Pacific Storm Parade, Atmospheric River Could Bring Flooding, Landslides, Feet of Cascades Snow in Washington, Oregon
Pacific Storm Parade to Last Into Weekend
An atmospheric river is set to bring flooding rain and feet of snow to Washington and Oregon.
At a Glance
A classic winter jet stream is set up over the North Pacific Ocean.
This jet stream will continue to steer a number of Pacific storms to the Northwest coast.
Repeated rounds of rain could lead to flooding in parts of Washington and Oregon.
Feet of Cascades snow is possible, raising the danger of avalanches.
One location in Washington state will likely tally rain every day in January.
A strong Pacific jet stream will continue to push a series of storms into the Pacific Northwest through Groundhog Day weekend, bringing days of rain that could trigger flooding and landslides in Washington and Oregon.
This nearly west-to-east jet stream spanning the North Pacific Ocean from Asia to western North America is a classic feature in the winter months, sticking out as a ribbon of high winds in both analyses and model forecasts.
As a result, a flight from Tokyo to San Francisco will take less time and use less jet fuel than the same trip in reverse.
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.
(Spanning the North Pacific Ocean, a strong jet stream will guide a number of storms toward the Pacific Northwest through at least Groundhog Day weekend.)
In this case, our forecasts suggest this parade of storms will primarily take aim on the Pacific Northwest and parts of British Columbia, Canada.
These Pacific storms could be accompanied by an atmospheric river late this week, a deep plume of moisture often associated with heavier rain events. It sometimes spans thousands of miles from Hawaii or the Western Pacific Ocean toward the West Coast.
Stormcast: How Much and How Long?
The latest system will bring rain, mountain snow, even a few thunderstorms to the Pacific Northwest Tuesday.
Current Radar and Satellite
After that, additional rounds of stormy weather will plague the region into Groundhog Day weekend, but there will be breaks in the precipitation at times. A storm system Friday into Saturday could tap into an atmospheric river as it hits western Washington.
(Deeper atmospheric moisture in this image is shown by plumes of yellow, orange and red contours. The surface pressure field (isobars) is also shown by white lines. Clouds are shown by various shades of white.)
This combination of Pacific storms is likely to wring out heavy rain across western Oregon and western Washington. Some of these areas could pick up 5 to 8 additional inches of rain through Sunday.
This could trigger flash flooding, river flooding and landslides, particularly in western Washington, where precipitation has been heaviest this month and rivers are already running high.
Snow and Rain Forecast
Parts of the Cascades, particularly in Washington, could receive well over another foot of snow.
The combination of strong winds and heavy, wet snow will likely lead to a high danger of avalanches in the Cascades, particularly in Washington.
Little rain and Sierra snow is expected for the Interstate 80 corridor in Northern California, and Southern California should stay dry, as well.
So while steady, soaking rain may not fall every day, our latest forecast has at least a chance of light rain or showers virtually every day through the weekend in both Seattle and Portland.