Bulletin d’avalanche

West Slopes Central

Northwest Avalanche Center
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Danger d’avalanche

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

Points saillants

Snowfall starts mid-morning and avalanche danger will increase throughout the day. You are most likely to trigger an avalanche in thick, wind-drifted pockets of snow on steep mid and upper elevation slopes. Search for heavier wind-affected deposits of snow and avoid those locations on high-angle slopes.

Problèmes avalancheux

  • Wind Slabs

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

    Wind slabs will develop throughout the day as snow continues to build. These slabs are likely to react to a human trigger in steep areas. Most avalanches will probably occur in shallow pockets less than a foot deep, but there is a small possibility that you could trigger a larger avalanche stepping down two or more feet to the late January crust (see the next avalanche problem). 

    Search for thicker, heavier drifts of snow and pillowy or textured surfaces. They’re oftentimes found on convex rolls, in gullies, and around rocky outcroppings. Steer clear of slopes steeper than 35 degrees where you encounter these wind slabs. 

    At or just beneath rollovers or cornices at the top of a slope are spots that wind slab avalanches oftentimes break at. 

    Photo: Dallas Glass

  • Persistent Slabs

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

    The West North and Stevens Pass Zones both reported avalanches failing on a faceted (weak, sugary) layer near the top of the late January crust, buried on 1/30. This layer of concern probably exists in the West Central Zone as well. Two to three feet of snow sits on top of the late January crust in most areas. 

    If you’re planning on traveling near another zone, check the adjacent forecast for more details. It is unclear how widespread this layer is, and it may be difficult to find, varying from one spot to another even on the same slope. If you notice whumphs and long shooting cracks they are clear indicators of unstable snow. Avoid steep slopes when you encounter those alarming red flags. The layer is most likely to avalanche in wind-affected areas. Avoid large, unsupported wind-loaded rolls on shady slopes, especially at upper elevation northerly aspects.  

    (1/31/2022)

    This small fracture occurred in the Stevens Pass zone. It failed on very weak faceted grains within a crust/facet sandwich just above the late January crust. Small whumphing was also observed on nearby slopes.

    Photo: Matt Primomo

Avalanche Discussion

Up to six inches of snow could fall during the day on Friday, and winds will increase as the day continues. Freezing levels are 3,000-3,5000ft, so you may encounter small wet loose avalanches in moist snow in below treeline areas. If you see rollerballs or small slides, avoid steep nearby slopes or the areas beneath them. 

If you get out into the West Central zone, tell us if you find any weak snow near the Late January Crust and if you saw any avalanches. You can submit an observation HERE.

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