Bulletin d’avalanche

Snoqualmie Pass

Northwest Avalanche Center
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Danger d’avalanche

Sun
Alpin
3 · Marqué
Limite forestière
3 · Marqué
Sous la limite
2 · Modéré
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Périmé — ce bulletin a expiré 6 months ago. Vous consultez des conditions passées, pas le bulletin en cours.

Points saillants

A well-documented weak snowpack structure exists at Snoqualmie Pass. These weak layers may be stressed by rising temperatures or recent wind loading. Choose terrain carefully and remember that all steep slopes are currently suspect.

Problèmes avalancheux

  • Persistent Slabs

    • Alpin
    • Limite forestière
    • Sous la limite forestière
    Probabilité
    Likely
    Taille
    1–2

    Multiple buried weak layers in the upper snowpack may not provide direct feedback to you as a traveler, but they exist and are capable of producing surprising avalanches. Slabs may break widely or even trigger remotely (from a distance) if these layers fail. The greatest uncertainty surrounding this problem remains the likelihood of triggering. 

    With recent wind-loading and now a warm-up on the horizon, avalanche activity on these layers could be on the rise. Earlier this week, we saw an uptick in activity as temperatures warmed in neighboring zones. Don't treat Saturday like a standard Snoqualmie day - this problem is different.

    Our normal tips and tricks for evaluating stability won't work. Uptrack tests, small test slopes, and even hand pits can't give you a sense for where or how these weak layers will fail. Your best management technique will be to avoid all open slopes over 30 degrees. That includes wind-loaded terrain and even large openings in treed areas.

    (2/27/2026)

    A widely-breaking avalanche in the neighboring West South zone. This one doesn't have a confirmed failure date, but you can bet it's persistent by how wide it is.

    Photo: Crystal Mountain Pro Patrol

  • Loose Wet

    • Alpin
    • Limite forestière
    • Sous la limite forestière
    Probabilité
    Possible
    Taille
    1–2

    With temperatures on the rise and more sunshine in the forecast, wet avalanche activity may follow. Look out for wet avalanches anywhere the snow surface is getting moist. If you see snow shedding from trees and rocks, or fresh pinwheels and rollerballs, then you'll know the snow surface is destabilizing and wet slides could soon follow.

    This avalanche problem is typically easy to manage, but with persistent weak layers lurking below the surface, it gets more complex. In addition to fanning out and growing in size as they descend, the threat now exists that they will trigger larger and more dangerous persistent slab avalanches. 

    If the mountains start to fall apart in the heat of the day, head for shaded, low-angled slopes, keeping aware of the terrain above you.

    (2/27/2026)

    As temperatures rose and filtered sunshine made it through the clouds, the snow surface started to destabilize, producing rollerballs and pinwheels on Friday, 2/27. Expect more widespread activity throughout the weekend.

    Photo: Jeff Tarshis

Avalanche Discussion

A well-documented weak snowpack structure exists at Snoqualmie Pass. Two persistent weak layers (the 2/13 buried surface hoar and the 2/7 crust/facet combo) can be found within the upper few feet of the snowpack. These layers have been responsible for whumpfing collapses, shooting cracks, and a handful of persistent slab avalanches in the Snoqualmie Pass zone since last weekend. 

Although it has been a few days since our last reported persistent avalanche activity at Snoqualmie Pass, that doesn't mean the problem has gone away. In the neighboring West South and Stevens Pass zones, these same layers have been very active this week.

With recent moderate-to-strong winds, there are surely lingering wind slabs near ridgelines or rocky features, such as the base of cliffs or confined chutes. Management of these slabs is largely the same as for the persistent slab problem: avoidance. You likely won't find one problem without the other. 

As we look forward to the upcoming weekend, the winds should die down and be replaced by sunshine and rising temperatures. This will add a layer of uncertainty and complexity to an already unsettling time in the mountains. How will the generally cold and weak upper snowpack respond to the warmth? The answer is unclear, but on Friday, minimal solar input moistened the snow surface, producing widespread rollerballs and pinwheels. There will certainly be similar, and likely more, of this activity on Saturday.

For those of you who are superstitious and like a bit of history, Chair Peak has produced very large and destructive avalanches twice in recent years, both on March 1st. In one instance, debris filled Source Lake, then started heading down the valley. We're not saying it's going to happen this weekend, but we do have a persistent slab problem...

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