Next Atmospheric River Arrives Saturday: Heavy Rain & Flooding Expected

FastCast—Saturday, Nov. 26 to Sunday, Nov. 27:

The next atmospheric river is expected to impact the area from Saturday morning to early Monday. It will be stronger than the Thanksgiving atmospheric river, and will cause another round of river flooding. Expect rain totals of 0.5-1.5 inches in the interior lowlands, 2-5 inches on the coast and in Whatcom & Skagit Counties, and 3-10 inches in the Olympics and Cascades. The Olympic rain shadow (from Seattle to Mount Vernon and the NE Olympic Peninsula) will receive lesser amounts of 0.05-1 inch. River flooding is expected on the Snoqualmie/Snohomish, Skagit, and Nooksack Rivers. The worst flooding will be on the Skagit (major) and Nooksack Rivers (moderate), as well as the Snoqualmie River in Snoqualmie Valley (moderate). Due to the atmospheric river, temperatures will rise to the mid-upper 50s through Sunday evening. Rain from this atmospheric river will taper by Monday afternoon.

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The next atmospheric river will impact the Pacific Northwest from Saturday morning to Monday morning, bringing heavy rain and river flooding. Below is the UW rain forecast through 4 PM Monday.

Expect 0.5 to 1.5 inches in the lowlands. Less (0.05-0.5”) will fall in the Olympic rain shadow. The most concerning aspect of this atmospheric river is 2-5 inches of rain in Whatcom & northern Skagit Counties and BC’s Lower Mainland. Expect 2-5 inches on the coast and 3-10 inches in the mountains. 

Below is the Advanced Hydrologic Prediction Service flooding forecast through Tuesday.

Moderate flooding will occur on both forks of the Nooksack River, major flooding will occur on the Skagit River, and minor to moderate flooding will occur on the Snoqualmie and Snohomish Rivers. 

Flood-weary NW WA & SW BC will likely have urban flooding in addition to river flooding. Urban flooding is possible around the area, especially in low-lying or poorly drained areas.

Additionally, breezy winds are possible around the region from Saturday evening through Sunday afternoon. Gusts up to 25-35 mph are possible, strongest near the water. Below is the wind gust forecast for Federal Way from the Windy app.

Showers will continue through Wednesday. Stay updated on this atmospheric river and other active weather on Twitter (click the Twitter icon on the right side of the blog).