Bulletin d’avalanche

Purcells

Jan 4 – 5, 2012Avalanche Canada
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Archivé · expiré 15 years ago

Danger d’avalanche

Fri
Sat
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
    1–5
    In the alpine and at treeline winds continue to redistribute storm snow into wind slabs. I'd be suspect of any open area, even below treeline. Wind slabs may be stiff, and have a hollow drum like sound beneath you.

  • Cornices

    • Alpin
    • Limite forestière
    • Sous la limite forestière
    Probabilité
    Possible
    Taille
    2–6
    Cornices may become weak with rising alpine temperatures. The load on the slope below may trigger the weak mid-December surface hoar layer initiating large to very large destructive avalanches.

  • Persistent Slabs

    • Alpin
    • Limite forestière
    • Sous la limite forestière
    Probabilité
    Possible - Likely
    Taille
    3–7
    A cohesive slab sits over a surface hoar weakness buried in mid-December. This layer is still touchy and susceptible to rider triggers. Avalanches on this layer will be large, destructive and may fracture across surprisingly far distances.

Confidence

Fair - Timing, track, or intensity of incoming weather is uncertain

Weather Forecast

As the cold front sweeps through the interior Wednesday afternoon we will see cooling temperatures and moderate precipitation amounts. Wednesday Night: Snow amounts 10-15cms. Ridgetop winds 40-50km/hr from the SW. Alpine temperatures near -3. Freezing levels down to 900m. Thursday: Snow amounts near 5cms. Ridgetop winds 40-50km/hr from the SW, switching to 30km/hr from the NW. Freezing levels at valley bottom. Friday/Saturday: A ridge of high pressure builds bringing cooling, and dryer conditions into Saturday.

Avalanche Summary

Natural activity has tapered off, but I'd still be suspicious of the mid-December layer susceptible to rider triggers (especially sledders) please don't rule this out yet.

Snowpack Summary

The region received a sweet little top up overnight of 10cms. In the alpine and at treeline this new snow is being blown onto lee slopes and terrain features adding to previous soft slabs and wind slabs. In sheltered locations this new snow buries the surface hoar that formed over the New Years. We'll date this the January 3 SH layer, the crystals reported to be up to 10mm. This may become a concern with increased load. Below the surface down 80-140cms lurks the mid-December surface hoar/ crust/ facet layer. This is a layer of concern. Test results on this are still variable in the moderate to hard ranges with sudden planar characteristics. It continues to be sensitive to large triggers like cornice fall and explosives. Between this layer and the bottom of the snowpack sits a well settled mid pack. At the bottom of the snowpack basal facets and depth hoar crystals live. These become a concern in thinner snowpack areas, and became reactive under the new load of the post-Christmas storms.

Régions couvertes