Bulletin d’avalanche

Purcells

Dec 23 – 24, 2014Avalanche Canada
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Archivé · expiré 12 years ago

Danger d’avalanche

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

Avalanche hazard is high. As it decreases over the next few days, conditions will remain very tricky.

Problèmes avalancheux

  • Storm Slabs

    • Alpin
    • Limite forestière
    • Sous la limite forestière
    Probabilité
    Likely - Very Likely
    Taille
    1–4
    A thick storm slabs sits over a predominant surface hoar layer which has been very touchy to rider triggers. With additional snow, natural avalanches are likely and human triggered avalanches are very likely.

  • Deep Persistent Slabs

    • Alpin
    • Limite forestière
    • Sous la limite forestière
    Probabilité
    Unlikely - Possible
    Taille
    3–5
    The new snow load continues to build and this could reawaken the Nov 9 layer at the bottom of the snowpack. In some parts of the region, large avalanches have been failing on a deeply buried weak layer.

Confidence

Fair - Forecast snowfall amounts are uncertain

Weather Forecast

A Pacific frontal system reaches the Interior Tuesday afternoon bringing snow overnight into midday Wednesday. Snow amounts will accumulate anywhere from 10-25 cm with lesser amounts in Northern locations. This will be accompanied by moderate west ridgetop winds, switching NW by the afternoon. Treeline freezing levels will hover around 1000 m. By Thursday an upper ridge will build behind the cold front bringing cooler conditions with mostly cloudy skies and light snow amounts. Friday will see a mix of sun and cloud with flurries and freezing levels at valley bottom.

Avalanche Summary

On Monday, numerous natural and skier triggered avalanches were reported from size 1-2.5 and failing on the buried surface hoar layer 30-60 cm down. In adjacent regions remotely triggered avalanches occurred from distances up to 40 m away, which may exist in certain locations where the surface hoar is more predominant in the Purcells. New snow and wind will add load to the upper snowpack and natural avalanche activity is expected. Best case scenario is the new storm snow will initiate a widespread natural avalanche cycle, however; if it doesn't reach its tipping point then it will likely be primed for rider triggers through the holiday period.

Snowpack Summary

New snow 10-25 cm, accompanied by moderate-strong SW winds will add additional load to the upper snowpack. This brings storm snow totals 40-80 cm above a very touchy surface hoar layer that was buried mid-December.  A lower layer of surface hoar is also reactive at the northern end of the range, buried down about 40cm.Below 2100 m this storm slab sits on a thick, solid crust that has been reacting as a perfect sliding layer. Storm slabs will blanket the region and be very touchy to the weight of a skier/ rider, especially in locations that has seen wind effect. A hard rain crust with facets from early November is buried over 1 m down and is still reactive to light loads in some locations.

Régions couvertes