Bulletin d’avalanche

South Rockies

Feb 8 – 9, 2012Avalanche Canada
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Archivé · expiré 15 years ago

Danger d’avalanche

Fri
Sat
Alpin
2 · Modéré
Limite forestière
2 · Modéré
Sous la limite
1 · Faible
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Problèmes avalancheux

  • Wind Slabs

    • Alpin
    • Limite forestière
    • Sous la limite forestière
    Probabilité
    Possible
    Taille
    1–3
    Fresh wind slabs are expected to develop below ridge crests and behind terrain breaks in lee and cross-loaded terrain.

  • Cornices

    • Alpin
    • Limite forestière
    • Sous la limite forestière
    Probabilité
    Possible
    Taille
    3–6
    Cornices are large, unsupported and may be a trigger for a large avalanche on the slope below.

  • Deep Persistent Slabs

    • Alpin
    • Limite forestière
    • Sous la limite forestière
    Probabilité
    Unlikely - Possible
    Taille
    3–6
    Deep and destructive persistent slabs have become less likely, but may be triggered with a large trigger (cornice fall, trenching sled); especially in unsupported, rocky terrain.

Confidence

Good - -1

Weather Forecast

Mainly cloudy with a chance of flurries for the forecast period. Possibly 10cm overnight Thursday in some parts of the region. Freezing levels are expected to remain in valley bottoms and winds should remain light, but gusty from the west.

Avalanche Summary

Throughout the weekend numerous highly destructive persistent deep slab avalanches involving basal facets and depth hoar occurred in the alpine and ran to valley bottoms (check out the Avalanche Image Gallery under the Library tab for some photos). These highly destructive avalanches remain possible with heavy triggers, such as airborne sled impacts and cornice falls, in thin areas on variable slopes peppered with tree's and rocks.

Snowpack Summary

In Elk Valley North and the Crowsnest, the average snowpack depth at treeline is 150 cms. In Elk Valley S and the Flathead the snowpack depth is closer to 2 m. The current snow surface is well on its way in becoming a dangerous weak layer once a sufficiently cohesive slab develops. Surface hoar is continuing to develop on sheltered slopes at all elevations combined with near-surface facets at lower elevations and surface crusts on sun-exposed slopes. A well settled and strong snowpack sits on weak basal facets and depth hoar, which seem to be fairly widespread throughout the region. This deep persistent weakness recently became active again with warm temperatures, but cooler temperatures have once again reduced the sensitivity to triggers. Highly unpredictable glide cracks are also opening up, generally on slopes with smooth ground cover. These full-depth gaping 'crevasses' could release without warning or act as a significant terrain trap.

Régions couvertes