Bulletin d’avalanche

Purcells

Jan 21 – 22, 2012Avalanche Canada
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Archivé · expiré 15 years ago

Danger d’avalanche

Mon
Tue
Alpin
3 · Marqué
Limite forestière
3 · Marqué
Sous la limite
2 · Modéré
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Problèmes avalancheux

  • Wind Slabs

    • Alpin
    • Limite forestière
    • Sous la limite forestière
    Probabilité
    Likely
    Taille
    1–4
    Moderate winds from saturday will have created touchy windslabs on lee features at higher elevations.

  • Persistent Slabs

    • Alpin
    • Limite forestière
    • Sous la limite forestière
    Probabilité
    Unlikely - Possible
    Taille
    4–7
    Two layers to watch: 1. Buried surface hoar, most likely triggered on steep, unsupported slopes amongst the trees. 2. Basal facets, triggerable from thin snowpack areas or by a very heavy load (cornice fall, airborne sled). Avalanches could be large.

  • Storm Slabs

    • Alpin
    • Limite forestière
    • Sous la limite forestière
    Probabilité
    Possible - Likely
    Taille
    1–5
    A classic recipe for storm slabs has evolved; particularly on the west side of the range: new snow falling with rising temperatures onto loose dry snow. Watch for deeper storm slab avalanches, especially in steep or convex terrain.

Confidence

Fair - Due to variable snopack conditions

Weather Forecast

Sunday: 5-8cm of snow / Moderate westerly winds / Freezing level at surfaceMonday: Light snowfall / Moderate westerly winds / Freezing level at surfaceTuesday: Moderate snowfall / Strong southwest winds / Freezing level at surface

Avalanche Summary

Recent observations include loose snow avalanches running in steep terrain and isolated skier-triggered wind slabs in the size 1-2 range. Avalanche activity slowed down towards the end of the week, but is expected to increase again in the wake of Friday night/Saturday's storm.

Snowpack Summary

New storm snow from friday night/saturday morning has built up over wind slabs in exposed features and over loose dry snow in sheltered areas. New snow amounts from friday's pulse were highly variable throughout the region. Lesser 24hr snowfall amounts were at about 6-10cm on the east side, and up to 25cm on the west side. Anomalous southeast moderate winds were observed in Golden, so expect irregular loading patterns at ridge top in that area. The mid-December surface hoar/facet persistent weakness, now down around 55cm on the eastern side of the range and as deep as 190cm on the western side, is still causing operators concern, especially in shallow snowpack areas. Recent snowpack tests show moderate to hard, sudden planar results on this layer. The consequences of a failure on this layer would be large. Facets and depth hoar exist at the base of the snowpack. Cornices are large and weak in some areas.

Régions couvertes