Pacific Northwest and Northern California brace for incoming atmospheric rivers

Two atmospheric rivers, long, narrow bands of moisture originating over the Pacific Ocean, are expected to bring a series of heavy rainstorms to the Pacific Northwest and Northern California.

The CW3E’s atmospheric river landing algorithm predicts these ARs will impact the region between late November 10 and 14.

The Weather Prediction Center (WPC) forecasts at least 76.2 mm (3 inches) of precipitation over the next seven days for the Cascades and coastal areas in Washington, Oregon, and Northern California. 

The heaviest precipitation, expected to exceed 254 mm (10 inches), is forecast for the Olympic Peninsula and portions of the Cascade Mountains, creating additional flood concerns for these areas. 

Rain may also affect the population in these states along riverbanks and low-lying metropolitan areas.

The first wave of storms will arrive with a surface cyclone propagating from the Central Pacific into the Gulf of Alaska, driving an atmospheric river into the Pacific Northwest on Monday, November 11. 

This will be followed by a second surface cyclone and atmospheric river shortly afterward, making landfall over the Pacific Northwest on November 12.

The heavy rain is expected to continue through November 14, with the peak rainfall forecast between November 10 and November 13.

The Global Ensemble Forecast System (GEFS) and the ECMWF ensembles have forecasted AR3 (moderate) and AR2 (mild) conditions for sections of Washington and Oregon, depending on the intensity and location of each atmospheric river. 

The Weather Prediction Center has issued alerts indicating at least a moderate chance (level 1 of 4) of flash flooding for coastal regions in Washington, Oregon, and California, covering 24-hour periods ending at 12:00 UTC from November 11 through 13.

References:

¹ Quick Look at the Heavy Precipitation over the Pacific Northwest and Northern California – CW3E – November 8, 2024

Harsha Borah

Harsha Borah is an experienced content writer with a proven track record in the industry. Harsha has worked with LitSpark Solutions and Whateveryourdose, honing skills in creating engaging content across various platforms. A gold medalist in a state-level writing competition organized by Assam Tourism, Harsha’s travelogue on Tezpur was widely appreciated. Harsha’s article, "The Dark Tale of the Only Judge in India to Be Hanged," ranks second on Google and has garnered over 11 000 views and 8 900 reads on Medium. Outside of writing, Harsha enjoys reading books and solving jigsaw puzzles.

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