Bulletin d’avalanche

Sea To Sky

Dec 17 – 18, 2011Avalanche Canada
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Archivé · expiré 15 years ago

Danger d’avalanche

Mon
Tue
Alpin
3 · Marqué
Limite forestière
2 · Modéré
Sous la limite
1 · Faible
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Problèmes avalancheux

  • Wind Slabs

    • Alpin
    • Limite forestière
    • Sous la limite forestière
    Probabilité
    Likely
    Taille
    1–3
    Fresh wind slabs will exist on lee and cross-loaded features at treeline and in the alpine. Size and reactivity should increase with forecast weather.

  • Storm Slabs

    • Alpin
    • Limite forestière
    • Sous la limite forestière
    Probabilité
    Likely
    Taille
    1–2
    As forecasted snow creates a consistent vail over the old surface from the December dry spell, expect storm slab development on a variety of aspects and elevations.

Confidence

Fair - Freezing levels are uncertain on Sunday

Weather Forecast

On saturday night and into sunday morning 10-15 cm of snow is forecast for the region with moderate to strong southwest winds. Freezing levels should sit at about 1200m during this time.During the day on sunday expect slight clearing, light northwesterly winds and freezing levels dropping to surface. On monday the forecast calls for continued clearing, light northwesterly wind and freezing levels at surface.On tuesday, expect more of the same with trace amounts of snow.

Avalanche Summary

Recent observations include several easily triggered pockets of fresh wind slab in immediate lee terrain near ridge crests. The size and likelihood of avalanches should increase with saturday night's forecast weather.

Snowpack Summary

The early December dry spell left us large surface hoar and faceted powder on sheltered shady slopes, and a surface crust on sun-exposed slopes. They are now buried by soft slabs and more recent wind-transported moist snow and will continue to get an increased load over the forecast period. Assuming the structure of the old snow surface is preserved long enough for a sufficiently thick and cohesive slab to bury it, then a highly unstable situation should develop. Particularly where surface hoar and/or faceted crystals are associated with a weak crust. The mid and lower snowpack are generally well settled and strong, but faceted. Basal facets and depth hoar necessitate caution on wind-exposed slopes with highly variable snowpack depths, where this deep persistent weakness could be triggered from a shallow spot. Check out the Forecaster's Blog link below for more general snowpack discussion and good advice.

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