Bulletin d’avalanche

South Columbia

Mar 17 – 18, 2016Avalanche Canada
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Archivé · expiré 11 years ago

Danger d’avalanche

Sat
Sun
Alpin
3 · Marqué
Limite forestière
3 · Marqué
Sous la limite
2 · Modéré
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Points saillants

Solar radiation and increasing freezing levels will increase natural avalanche activity. Avoid slopes with overhead exposure where falling cornices could trigger large avalanches.

Problèmes avalancheux

  • Cornices

    • Alpin
    • Limite forestière
    • Sous la limite forestière
    Probabilité
    Possible - Likely
    Taille
    2–5
    Daytime warming and solar radiation will promote large cornice failures which could, in turn, trigger a large avalanche on the slope below.

  • Persistent Slabs

    • Alpin
    • Limite forestière
    • Sous la limite forestière
    Probabilité
    Possible
    Taille
    3–6
    The late February layer is becoming less likely to trigger, but it continues to surprise riders with large avalanches. I'd aim for well-supported slopes without convexities, and I'd be increasingly cautious as solar radiation comes into play.

  • Loose Wet

    • Alpin
    • Limite forestière
    • Sous la limite forestière
    Probabilité
    Likely - Very Likely
    Taille
    1–4
    As the sun comes out, surface avalanche conditions will include a mix of wind slabs in high elevation lee terrain, and pushy loose wet activity on steep, sun-exposed slopes. Loose wet avalanches may also trigger deep and destructive slab avalanches.

Confidence

High

Weather Forecast

The ridge over the province begins to break down on Friday with increasing clouds on Saturday and perhaps some flurries on Sunday.  Expect winds to be generally light and southerly.  The BIG news in the increasing freezing levels on Saturday(~2000m) which may be followed by poor crust recovery Saturday night and even higher freezing levels on Sunday(~2200m).

Avalanche Summary

On Wednesday, a skier triggered a size 2.5 slab avalanche on a southeast aspect at treeline(~2200m). There were several additional natural and cornice triggered slab avalanches to size 2.5 on a variety of aspects in the alpine and at treeline. Solar radiation and increasing freezing levels will be the main driver of natural avalanche activity in the coming days.

Snowpack Summary

At ridgetop, cornices are huge and could be become increasingly touchy with forecast solar radiation. On lee features at treeline and in the alpine light amounts of new snow overlie older wind slabs while sunny skies have promoted a melt-freeze cycle on sun-exposed slopes. 60-110cm below the surface you'll find a persistent weak layer comprised of surface hoar, facets and/or a thick crust. This layer, which was buried on February 27th, seems variably reactive. In other words, it's still touchy in some places while in other places it's really tough to trigger, and there's not much of a reliable pattern telling us what exact aspects are most suspect. I'd continue to be suspicious of steep, unsupported features at treeline and in the alpine as this layer has the potential for very large avalanches. Below this interface, the snowpack is generally gaining strength.

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