Bulletin d’avalanche

Snoqualmie Pass

Northwest Avalanche Center
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Danger d’avalanche

Wed
Alpin
2 · Modéré
Limite forestière
2 · Modéré
Sous la limite
1 · Faible
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Périmé — ce bulletin a expiré 5 years ago. Vous consultez des conditions passées, pas le bulletin en cours.

Points saillants

Even as the relatively quiet weather gives the snowpack time to gain strength you may still encounter avalanche risk in wind affected snow and in very large avalanche paths. Choose terrain where you feel confident and comfortable in your ability to reduce your risk through where and how you travel.

Problèmes avalancheux

  • Wind Slabs

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

    Several travelers observed thin wind slabs at mid and upper elevations on Sunday. Even though these drifts are a few days old, you may still trigger them on steep slopes below cornices, near rocks, or in confined chutes. The look and feel of the surface snow could serve as your best indication of wind-affected snow. When you see a textured surface or feel slightly firmer/deeper snow, anticipate wind slabs on similar slopes. Don’t let these shallow avalanches surprise you and carry you over cliffs or into rocks. Even small avalanches can prove deadly when they involve terrain traps.

    (3/7/2021) Textured snow surfaces like this can help you anticipate which slopes or features could harbor wind slabs. Photo: Ian Nicholson

  • Deep Persistent Slabs

    • Alpin
    • Limite forestière
    • Sous la limite forestière
    Probabilité
    Unlikely
    Taille
    3

    Despite the lack of avalanche activity over the past week, the deep persistent weak layer continues to stay front and center on our minds. It’s hard to get the images of the massive avalanches and their destruction out of our heads (See Media Gallery below). Recent weather patterns and a strengthening upper snowpack helped build our confidence over the past few days. However, we know the consequences of an avalanche on this layer remain dire. If you choose to travel in larger and more complex avalanche terrain, talk openly with your team about the low-likelihood/high-consequence risk. Limit the amount of time you spend in and under large avalanche paths. This includes areas well below treeline where these beasts may run or stop. 

    (3/1/2021) Looking down at Source Lake where debris over-ran the lake and the berm. This is a popular lunch spot for skiers, snowshoers, and hikers. These large slides are running far distances toward valley bottoms. [Photo: Jonathan Spitzer]

Avalanche Discussion

A bit of uncertainty exists regarding the cloudy cover in Tuesday’s weather forecast. We expect mostly cloudy skies, but during spring patterns like this the weather can surprise you. If you encounter more sunshine, anticipate the chance for a few small natural loose avalanches on steep slopes. New rollerballs and the snow shedding from rocks and trees should give you a warning. If you see these clues, use caution around similar slopes basking in the sun. 

The pass received 4-8” of snow this past weekend. Windy weather reshaped much of the surface, creating deeper drifts and scoured slopes on exposed areas mid and upper elevations. The recent snow accumulated over a new and strengthening crust (3/5). Below this layer you should find a generally strong and well-settled snowpack. While you can still find many of the interfaces and crusts discussed over the past month, the layer to watch remains the mid-January facet-crust combination. This layer sits 8-10+ft below the snow surface. The last known avalanche occurred on this layer 2/28-3/1 on Chair Peak. It and similar slides broke numerous trees and descend to near their historical runout zones. Don’t let this deep persistent layer drop from your mind just yet. 

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.

Régions couvertes