Small pockets of 50% or better odds on 4 inches or more of snow cover the highest Olympics and northern Cascades through the end of October, according to the National Weather Service’s Weather Prediction Center. The probabilities sit in the center’s Probabilistic Heavy Snow and Icing Discussion, written by forecaster Weiss and issued at 1752Z on Oct. 28, 2026, about 1:50 p.m. Eastern time. The product is valid from 00Z Oct. 29, which is 5 p.m. Pacific daylight time on Wednesday, to 00Z Nov. 1, which is 5 p.m. Pacific on Saturday, Oct. 31.
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A closed low offshore and a 4,000-foot snow line
The pattern behind the snow is a closed mid-level low offshore of Washington, which the forecast has delivering snow to the Olympics, Cascades and Northern Rockies into Friday, mainly above about 4,000 feet.
Weiss described a modest event rather than a major one. Moisture is near normal, and the strongest lift fades early in the first forecast day, so additional accumulation should be limited, according to the Weather Prediction Center’s discussion. Even so, the text calls out “small pockets of 50%+ probabilities of 4 inches or more in the highest Olympics, northern Cascades, and Northern Rockies,” a phrase that confines the 50% contour to the tallest terrain and attaches no such odds to the lower slopes.
The Seattle forecast office laid out the earlier half of this storm before the national window opened. In its area forecast discussion issued at 926 a.m. PDT on Monday, Oct. 26, NWS Seattle/Tacoma expected snow levels to fall to 2,500 to 3,500 feet from Tuesday evening into Wednesday morning. The discussion put the passes at “between 4-6 inches” and the higher peaks at “8-13 inches by Wednesday evening.” The national probabilities pick up at about the moment those Wednesday totals were due to be complete, which is why the later numbers read as a tail on a storm already under way rather than a fresh onslaught.
Farther east, NWS Missoula’s 12:42 p.m. MDT discussion on Oct. 26 placed the heaviest snow across the Mission Mountains and up into Glacier National Park, matching the Northern Rockies pocket in the national text. Snow levels there were forecast near 4,000 to 5,000 feet, dropping to about 3,000 feet along Highway 2 by Thursday.
The calendar inside the discussion limits when the snow has to fall. Its Northern Cascades and Northern Rockies section covers Days 1 and 2, and each forecast day runs 24 hours from 00Z. Day 1 therefore spans 5 p.m. PDT Wednesday to 5 p.m. PDT Thursday, and Day 2 runs to 5 p.m. PDT Friday. Any 4-inch total in the highest Olympics and northern Cascades has to come together in those 48 hours, while the strongest lift is already fading, which helps explain why Weiss kept the 50% contour down to small pockets.
Reading a 50% chance of 4 inches
The center’s snowfall probabilities express the chance that snow reaches or exceeds a stated amount, for each of the first three forecast days. On the winter weather product page, the final thresholds are 4, 8 and 12 inches, which makes 4 inches the lowest rung of the ladder. A pocket of 50% or better at 4 inches therefore says the odds of reaching that first rung are even or better. It carries no claim about 8 or 12 inches, and the discussion cites only the 4-inch figure for the Northwest.
Weiss placed those odds in the highest terrain only. Ground below the summits is not part of the 50% pockets in the text.
Point forecasts come from a different desk. The same product page notes that specific snow amounts are drawn from the National Weather Service’s National Digital Forecast Database, a gridded record kept apart from the probability charts. For a particular trailhead or pass, the forecast-office products are therefore the finer-grained record, with the national probabilities from the College Park, Maryland-based Weather Prediction Center acting as the regional frame around them.
Ice odds and a cool, drier weekend on the west side
The discussion also puts the probability of significant ice across the contiguous United States below 10 percent for the whole period. Freezing rain therefore drops out of the Northwest picture, leaving snowfall at elevation as the hazard the Olympics and Cascades section of the text addresses.
Seattle’s Oct. 26 discussion looked past the storm as well. The office forecast lower chances of precipitation for Western Washington as the upper low deepens offshore, with highs in the upper 40s to low 50s and lows in the 30s, dipping to the upper 20s in colder spots. The product made no weekend snow forecast for the Olympics or Cascades, and it gave no snowpack outlook, so the weekend picture for the mountains rests on the national center’s window.
The national window closes at 00Z Nov. 1, and later issuances will supersede the 1752Z discussion. Whether the 4-inch pockets verify will show in Seattle’s next discussions and in the center’s updated charts. As written on Oct. 28, the call from Weiss was narrow: the highest terrain, 50% or better, 4 inches or more, with snow mainly above about 4,000 feet.
This article was produced with the assistance of AI and reviewed by Morning Overview editors prior to publication.
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