Bulletin d’avalanche

Northwest Coastal

Dec 19 – 20, 2012Avalanche Canada
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Archivé · expiré 14 years ago

Danger d’avalanche

Fri
Sat
Alpin
3 · Marqué
Limite forestière
2 · Modéré
Sous la limite
2 · Modéré
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Points saillants

Problèmes avalancheux

  • Persistent Slabs

    • Alpin
    • Limite forestière
    • Sous la limite forestière
    Probabilité
    Possible
    Taille
    2–5
    A persistent weak layer of surface hoar, buried 60-80 cm below the surface, has been reported from around Shames. The chance of avalanche activity on this layer may increase as the slab above it gets stiffer.

  • Storm Slabs

    • Alpin
    • Limite forestière
    • Sous la limite forestière
    Probabilité
    Likely
    Taille
    1–4
    Variable amounts of new snow will likely be sensitive to human triggers, particularly in wind-exposed terrain. Natural avalanches are possible, particularly on northwest through east aspects.

  • Deep Persistent Slabs

    • Alpin
    • Limite forestière
    • Sous la limite forestière
    Probabilité
    Unlikely - Possible
    Taille
    3–7
    Deeply buried weaknesses exist. Large triggers, such as cornice falls, could release deeper avalanches on steep, smooth terrain, especially in thinner snowpack areas.

Confidence

Fair - Due to variable snowpack conditions

Weather Forecast

Overnight Wednesday and Thursday: Light to locally moderate snowfall and strong southeast windsFriday: Mix of sun and cloud / Moderate to strong east winds Saturday: Mostly clear with light east windsFreezing level is expected to remain at surface for the forecast period

Avalanche Summary

On Tuesday explosives controlled slabs to size 3 were triggered in the north of the region. Some of these releases failed on basal facets. There have also been a few releases to size 2 failing within recent storm weaknesses.

Snowpack Summary

Up to 65cm of recent storm snow is settling rapidly, although weaknesses still exist within storm snow interfaces. A buried surface hoar layer, reported to be 5 to 10mm thick, recently produced sudden snowpack test results down 60-80cm in the Shames backcountry, and may exist in other areas too. Avalanche professionals continue to monitor a faceted crust near the ground. It seems this problem is confined to alpine areas and likely needs a large trigger and/or a shallow snow pack feature to trigger. Cornices are also really big and forecast strong winds and cooling temperatures could make them especially heavy and brittle.

Régions couvertes