Persistent Slabs
- Alpine
- Treeline
- Below treeline
- Likelihood
- Likely
- Size
- 2–2.5
Recent Avalanches: There have been no reports of avalanches since Friday when we had several large natural avalanches in Seattle Ridge (Main Bowl, weather station bowl, Jr’s, Warm-Up Bowl). There was also a human triggered avalanche on Sunburst and several remote triggered avalanches in the Tincan trees (observations are here and here).
We should have our guard up if we are getting into the backcountry today. It has been four days since we had a widespread avalanche cycle where large avalanches were failing on one of several buried weak layers 1 to 3' deep. This unstable snowpack has been seen up to the ridges meaning it is on many slopes. We heard a report that the rain line reached at least 2,200' which may eventually make these layers harder to trigger where a rain crust forms, but it is still not a snowpack setup we can trust.
Approach the mountains with caution today. It can be tough to assess how dangerous the snowpack is on the slope you want to ride. With weak layers like these it is possible to ride the slope a few times, or to get stable results in snow tests only for the slope to rip out as a large avalanche. When the snow is tricky it's best to give it time to gain strength and enjoy lower angle slopes.
Wind Slabs: The storm overhead will likely form small wind slabs below ridges and convex rollovers. If you see wind blown snow be aware that wind slabs are forming. More importantly, triggering a wind slab avalanche could also trigger one of these deeper weak layers creating a much larger avalanche. You will likely be traveling on a wind slab if the snow below you is stiff and sounds hollow. Your best bet is to turn around and find softer snow sheltered from the wind.
(11/28/2025)
Skier triggered avalanche on Sunburst.
Photo: Public