Bulletin d’avalanche

South Rockies

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

Danger d’avalanche

Fri
Sat
Alpin
4 · Fort
Limite forestière
4 · Fort
Sous la limite
3 · Marqué
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Points saillants

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Problèmes avalancheux

  • Wind Slabs

    • Alpin
    • Limite forestière
    • Sous la limite forestière
    Probabilité
    Likely - Very Likely
    Taille
    2–6
    Wind slabs may be found on lee slopes, 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
    1–6
    Storm slabs will continue to build through the forecast period. 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 - Intensity of incoming weather is uncertain on Saturday

Weather Forecast

Continued unsettled, stormy weather conditions through the South Eastern parts of the province. A strong SW flow, moderate snowfall amounts and rising freezing levels will prevail. Thursday: Snow amounts 10-20 cm. Ridgetop winds strong from the SW. Treeline temperatures near 2 degrees. Freezing levels 1800 m. Friday/Saturday: Snow amounts light-moderate. Ridgetop winds will remain strong from the SW. Freezing levels 1800 m, falling to 1200 m on Saturday.

Avalanche Summary

On Tuesday explosive controlled avalanches up to size 1.5 were reported. 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. With forecast snow, wind and warming; I expect the region will see another natural avalanche cycle.

Snowpack Summary

Recently the region has received 30-40 cm of new snow. Touchy storm slabs exist at all elevations. Strong SW winds have created stiff 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 destructive 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