Bulletin d’avalanche

South Rockies

Mar 13 – 14, 2012Avalanche Canada
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Archivé · expiré 15 years ago

Danger d’avalanche

Thu
Fri
Alpin
4 · Fort
Limite forestière
3 · Marqué
Sous la limite
3 · Marqué
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Problèmes avalancheux

  • Wind Slabs

    • Alpin
    • Limite forestière
    • Sous la limite forestière
    Probabilité
    Likely
    Taille
    2–6
    Wind slabs may be lurking behind ridges and terrain breaks.

  • Persistent Slabs

    • Alpin
    • Limite forestière
    • Sous la limite forestière
    Probabilité
    Possible - Likely
    Taille
    3–7
    A persistent weak layer around 1m deep has the potential to produce large and dangerous avalanches. It could be triggered by the weight of a person, remotely or in surprisingly mellow terrain. It is tricky to manage this problem, so be conservative.

  • Storm Slabs

    • Alpin
    • Limite forestière
    • Sous la limite forestière
    Probabilité
    Likely - Very Likely
    Taille
    2–6
    Storm slabs are building deeper with each successive weather system. Loose sluffs are also a possibility in steep terrain. Storm slabs and sluffs could step down to a persistent weak layer, creating destructive avalanches.

Confidence

Fair - Timing, track, or intensity of incoming weather is uncertain for the entire period

Weather Forecast

The timing of a series of fronts affecting the region is uncertain. Wednesday: Cloudy with clear breaks. Snow developing in the afternoon or evening. Freezing level around 1000m.Thursday/Friday: Light to moderate snow. Freezing level around 1200-1500m. Variable south-westerly winds.

Avalanche Summary

On Monday, skiers triggered size 1-1.5 soft slabs in steep terrain. A widespread natural avalanche cycle occurred up to size 3 in response to very warm temperatures and loading of start zones by strong winds on Friday and Saturday. Video footage here: https://bit.ly/yR4E8r . On Friday, a snowmobiler was killed in a size 3 slab on a south-west aspect at treeline in the Corbin Creek area and a skier was injured in an avalanche in steep terrain in the Flathead Range. Over the last week, there were several reports from in or near the region of near misses, including a snowmobiler who triggered an avalanche and was buried for around 30 minutes, remote-triggered avalanches, and slab avalanches running into unusually low-angled terrain.

Snowpack Summary

Storm snow continues to build up. South-westerly winds are likely to have created wind slabs behind ridges and terrain breaks. The mid February surface hoar layer in the upper snowpack is most prevalent in the west and south of the region, particularly in the Flathead. Recent snowpack tests, as well as rider-triggered avalanches, on this weak layer indicate that it still has the potential to be triggered in many areas, resulting in a large avalanche. Remote-triggering, triggering from below and triggering on low-angled terrain are also concerns. Basal facets may still exist, particularly in shallower snowpack areas with steep, rocky start zones. Cornices have grown large and threaten slopes below. Conditions are variable across the region.

Régions couvertes