Bulletin d’avalanche

South Coast

Dec 12 – 13, 2016Avalanche Canada
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Archivé · expiré 10 years ago

Danger d’avalanche

Tue
Wed
Alpin
2 · Modéré
Limite forestière
2 · Modéré
Sous la limite
1 · Faible
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Points saillants

It's not coastal cement: the cold storm means instabilities will persist longer than is usual for this region. Be very cautious if you are considering venturing into steep terrain.

Problèmes avalancheux

  • Wind Slabs

    • Alpin
    • Limite forestière
    • Sous la limite forestière
    Probabilité
    Possible - Likely
    Taille
    1–2
    Heavy snowfall has created touchy wind slabs which are expected to remain reactive to human triggering. In many areas, the storm snow likely sits over a weak layer which may prolong the reactivity of these slabs.

Confidence

Moderate - Due to the number of field observations

Weather Forecast

Tuesday, Wednesday and Thursday: Clear, cold and dry. Treeline temperatures around -8C, winds light, initially from the northeast, becoming easterly on Wednesday. Some cloud appearing Thursday.

Avalanche Summary

On Sunday two skiers were caught in an avalanche on the North Shore on Sunday in steep, rugged terrain. There's a photo on the North Shore Rescue Facebook page. On Saturday, a size 1.5 skier triggered avalanche was reported on the MIN. The slab was 20-30cm thick and the avalanche was 30-40m wide. Other social media from the weekend indicated highly unstable conditions. With dry, cold weather, avalanches will become harder to trigger, but I'd urge caution, since the cold temps will prolong the possibility of skier-triggered avalanches longer than is usual for this region.

Snowpack Summary

Highly variable snowfall amounts were reported across the region. In the deepest areas in the south of the region, upwards of 1 m of new storm snow accumulated over the weekend; closer to Squamish, it was more like 30 cm. The new snow sits on an old surface that was highly variable and may include well settled snow on southerly aspects, loose snow on shaded aspects, isolated pockets of surface hoar, and sun crusts on steep solar aspects. The nature of the bond between the new snow and old is critical right now. Colder than usual temperatures mean this interface will take longer than normal to stabilize. There may be isolated pockets of buried surface hoar that could act as a good sliding layer in open sheltered areas. Wind slabs can be expected behind exposed, wind-loaded terrain features. An old rain crust is reported to be buried 110-120 cm below the surface in the North Shore mountains. This layer is still failing on snowpack tests, but is likely difficult to trigger in most places now. Below the crust, the snowpack is well settled and strong.

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