A series of atmospheric rivers is pushing rain and mountain snow into the Pacific Northwest

Rain returns to the Pacific Northwest tonight and keeps arriving in waves into next week, with forecasters in Seattle and Portland describing a run of fronts rather than a single storm. Atmospheric river moisture is expected to ride along with at least part of the sequence, and mountain snow enters the picture once snow levels fall on Sunday. Totals so far look modest next to the region’s wettest autumn events.

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Travelers on the passes, boaters along the coast and anyone watching whether the storm track eventually sags toward California all have reasons to follow how the pattern develops over the next several days.

Gulf of Alaska storms and the West Coast trough

The newsletter Weather Trader, run by meteorologist Ryan Maue, framed Wednesday’s pattern in blunt terms: a parade of powerful Gulf of Alaska storms and atmospheric rivers that “gets underway for quite a while.” The same post noted that a series of troughs keeps dipping down the West Coast and floated California as a possible target in roughly ten days, a horizon well beyond what local forecast offices will commit to. Because the newsletter is a secondary source, the federal forecast products below carry the specifics.

NOAA’s Climate Prediction Center pointed in the same direction in its 8-14 day prognostic discussion issued October 26, which covered November 3 through 9 and described a trough stretching from the Bering Sea and Aleutians southeastward to the West Coast, with a second trough sitting upstream off the coast. Such geometry steers Gulf of Alaska systems toward Washington and Oregon. The center’s 8-14 day outlook page was refreshed on November 4 and now covers November 12 through 18.

The Climate Prediction Center’s precipitation language adds a longer view. In that October 26 discussion, forecasters favored above-normal precipitation for the overwhelming majority of the Lower 48 in the 8-14 day window, with probabilities above 50 percent over western Oregon and northern and central California. The accompanying state table for the same window listed below-normal precipitation for every state, a conflict the narrative text does not explain, so the discussion is best read as a signal about the storm track rather than a rain total for any one city.

Seattle’s sequence of fronts through Monday

The National Weather Service office in Seattle laid out the timing in an area forecast discussion issued at 3:27 p.m. PST Wednesday. A weak front brings a few hours of steadier rain tonight, with up to 0.15 inch for most of Puget Sound and 0.25 to 0.5 inch along the coast. Thursday offers a break. A stronger system arrives Thursday night into Friday with steadier rain and gusty south winds that could reach Wind Advisory levels on the northern coast and north of Whidbey Island, and the heaviest amounts fall on the Cascades and the Olympic Peninsula.

Wind and surf are the other half of the Seattle forecast. Friday’s gusty south winds are aimed at the northern coast and the area north of Whidbey Island, where Wind Advisory levels are possible, and Sunday’s cold front brings the rough seas. Neither the Seattle nor the Portland text carries flood language, and the rainfall numbers are small enough that the main impacts look like slick roads, gusty exposed stretches and a wet weekend for anyone heading to the coast or the passes.

Saturday is a warm-sector day, drier by afternoon except near the Olympics and the British Columbia border. The bulk of the rain and the gustiest winds come with a cold front from Saturday night into Sunday, when seas near 20 feet are expected on the coast. After a brief lull Sunday night into Monday, the forecaster, who signed the product only as JD, wrote that additional systems are possible through midweek, with ensemble guidance divided enough that a longer-duration rain event cannot be ruled out.

Portland’s rain odds, snow levels and the atmospheric river label

NWS Portland’s discussion from Tuesday afternoon is the one that uses the phrase directly. Forecasters there wrote that the northern jet “will likely be associated with atmospheric river moisture,” which bears on whether Friday turns wet or stays dry. Even so, the office kept amounts in check: mean precipitation around 0.10 to 0.30 inch, with a 20 to 40 percent chance of topping half an inch along the coast and 30 to 45 percent in the south Washington and north Oregon Cascades and foothills. Its summary was that amounts remain relatively low, and it added that “the hits keep on coming” because another front could cross on Saturday.

Snow is the slower story. Portland put snow levels near 5,000 to 6,000 feet before lifting again this weekend, and Seattle has them starting Saturday around 8,000 feet before the Sunday cold front drags them down to roughly 4,000 to 5,000 feet over the Cascades and Olympics. In practical terms, the mountains mostly see rain through Saturday, then a shot at accumulating snow at the higher passes late Sunday, with no sustained snow event in either office’s text so far.

Terminology is where the sources split. Seattle’s discussion never uses the words atmospheric river, Portland says the moisture is likely to be of that type, and Weather Trader states it flatly. The label is plausible for the strongest pulses, with the Friday and Sunday fronts the likeliest candidates, while the weaker Wednesday-night front looks like ordinary Pacific rain. The question forecasters were still monitoring Wednesday afternoon is whether the Monday-through-midweek systems that Seattle flagged stack into one longer soaking or fizzle between waves.

This article was produced with the assistance of AI and reviewed by Morning Overview editors prior to publication.

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