Bulletin d’avalanche

West Slopes Central

Northwest Avalanche Center
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Danger d’avalanche

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

Points saillants

Avalanches are very likely in the storm snow falling Friday night through Saturday. Stick to lower angle terrain as the storm runs its course. Steer well away from the bottom of steep avalanche paths as well, even if the terrain is flat where you are.

Problèmes avalancheux

  • Loose Wet

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

    Warmer temperatures at lower elevations could lead to wet snow conditions. Rollerballs and small loose wet avalanches are likely to occur in the wet snow surface. When you start noticing small rollerballs running down a slope, this may be a precursor to wet loose avalanches. Stay off steep slopes when you notice rollerballs frequently rolling down a slope and picking up more snow as they roll. 

    An example of rollerballs, an indicator that wet loose avalanches could start coming down.  Photo: Matt Primomo

  • Storm Slabs

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

    We're getting a lot of water, warming temperatures, and plenty of wind during this storm. Just one of those factors may be enough to cause a spike in avalanche danger, but all three combined definitely makes the alarm bells go off. This is a great recipe for avalanches.  

    Very dangerous avalanche conditions exist as this storm deposits several inches of snow in the mountains. Temperatures will rise as the storm continues on Saturday. Increasing temperatures as snow falls creates an “upside down” snowpack, which leads to heightened avalanche concerns. This means that snow at the surface is thicker and heavier than the snow beneath it. The heavier snow forms a slab that could easily slide on the lighter snow beneath it. Strong winds will redistribute snow at upper elevations into thicker and more reactive slabs.

    Feel for a "punchy" snowpack as you step, where heavier snow overlies lighter snow. Watch for obvious clues such as cracking, collapsing, and recent avalanches. The incoming snow may tip the scale on avalanches very quickly, before you even have a chance to register the change. Given all these factors, give avalanche terrain a wide berth on Saturday. You can still get out and play in lower angle terrain away from large overhead avalanche paths. 

     

    (12/16/2021)

    A recent example of a storm slab avalanche in a neighboring zone. 

    Photo: NWAC Public obs

Avalanche Discussion

There is a lot of uncertainty and unknowns with several of the factors of this approaching storm. Tread carefully in the backcountry during this storm. Continue to stay alert for early season hazards such as creeks, trees and rocks in lower elevation areas. They may become more pronounced as lower elevations will probably have a net loss of snow cover in the next 24 hours. 

Régions couvertes