Boletín de aludes

Stevens Pass

Northwest Avalanche Center
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Peligro de aludes

Mon
Alta montaña
2 · Moderado
Límite del bosque
2 · Moderado
Bajo el límite
2 · Moderado
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Desactualizado: este boletín caducó 5 years ago. Estás viendo condiciones pasadas, no el boletín vigente.

Lo esencial

Very large and dangerous deep persistent slab avalanches are still possible. Avoid large, steep open slopes at upper elevations and the runouts beneath them. A few inches of snow may create small wind slabs, which you might find on upper elevation leeward slopes.

Problemas de aludes

  • Deep Persistent Slabs

    • Alta montaña
    • Límite del bosque
    • Bajo el límite del bosque
    Probabilidad
    Possible
    Tamaño
    3–4

    Deep persistent slab avalanches have a low probability of occurring, but if one does, consequences are high. For this reason, maintain a conservative mindset as you travel in the backcountry.  Uncertainty remains as to when or if these avalanches will come down. The last recorded one was on March 1, but enough evidence exists that we are not yet ready to remove this problem.  Avoid going into, or underneath open or sparsely treed terrain with large start zones above you. 

    This deep persistent weak layer formed mid January, and is now buried 6-10+ feet deep. We’ve seen avalanches failing on this layer for well over a month now. Slopes of greatest concern are east, south and west aspects above 5000ft. The most likely way that an avalanche will occur is if a cornice were to fall onto a suspect slope beneath. Cornices are growing excessively large and are ripe for failure. Don’t tempt fate by stepping anywhere near the edge of one, or traveling in an area beneath a largely corniced ridge. 

    (2/25/2021) This deep slab avalanche (D4) ran naturally on 2/22 from a path known as Gaynor above Highway 2, east of Stevens Pass.

  • Wind Slabs

    • Alta montaña
    • Límite del bosque
    • Bajo el límite del bosque
    Probabilidad
    Possible
    Tamaño
    1

    You may encounter small reactive wind slabs as a few inches of snow falls Saturday night through Sunday. They may not be large enough to bury you, but if you are near terrain traps they could still pose a large enough threat. Pay attention to the snow surface as you gain elevation. Feel for firmer snow surfaces, and observe wind effects such as textured surfaces to identify where the wind loading occurred. Smaller, more confined steep slopes that may not have as much of a deep persistent slab risk could have wind slabs on them, so be sure to investigate to determine how readily they will slide before exposing yourself to the terrain. 

    (12/24/2020) Cracks in recently drifted snow are signs that an avalanche might occur if the slope is steep enough.

Avalanche Discussion

In the last week several deep slab avalanches surprised us.  On Monday, WSDOT avalanche teams triggered an 8ft deep D3 avalanche on the southeast face of Rock Mountain east of Stevens Pass (our last avalanche known to have failed on the persistent weak layer). In the Chiwaukum Mountains, a natural D3.5 avalanche in upper-elevation north-facing terrain is suspected to have run on Sunday. A massive avalanche (D4) ran naturally in the West Camp path on Rock Mountain just over a week ago. Viewing the tree-laden debris gives you a taste of the destructive potential of that avalanche as you drive along Highway 2 east of Stevens Pass.  

Given the abundance of uncertainty, forecasters remain concerned about the potential for very large avalanches. We're in a prolonged period of historically unstable conditions, dealing with a weak layer that has challenged even seasoned professionals. The deep slab problem continues to pose high consequences and demands conservative terrain and travel choices from all of us. 

During the ongoing Covid-19 pandemic, continue to follow the latest guidance from local, state, and federal health officials. Avoid unnecessary risks that could impact first responders and stress medical resources.  Wear a mask when appropriate, practice social distancing, and consider recreating closer to home.

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