Bulletin d’avalanche

Sea To Sky

Jan 23 – 24, 2012Avalanche Canada
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Archivé · expiré 15 years ago

Danger d’avalanche

Wed
Thu
Alpin
4 · Fort
Limite forestière
4 · Fort
Sous la limite
4 · Fort
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Problèmes avalancheux

  • Wind Slabs

    • Alpin
    • Limite forestière
    • Sous la limite forestière
    Probabilité
    Very Likely - Certain
    Taille
    1–5
    Heavy snowfall amounts and strong winds will set up touchy new wind slabs. Due to strong winds, wind slabs may form in unsuspecting places lower on the slope.

  • Storm Slabs

    • Alpin
    • Limite forestière
    • Sous la limite forestière
    Probabilité
    Very Likely - Certain
    Taille
    1–5
    Heavy amounts of storm snow have fallen on existing cold, low density snow. This has set up an unstable situation in the upper snowpack. With forecast heavy precipitation, strong wind, and rising freezing levels we can expect storm slab avalanches.

Confidence

Good - -1

Weather Forecast

Tuesday: Warming, rising freezing levels and strong winds are forecast. Up to 40mm of precipitation is expected with freezing levels up to 1500m later in the day then falling back to 600m. Ridgetop winds will be 80km/hr from the SW. Wednesday: Heavy precipitation continues 25-35mm. Freezing levels near 800-1000m. Thursday: Strong winds will taper off early in the day, few flurries expected as a ridge builds across the region.

Avalanche Summary

Evidence of natural avalanche activity occurred overnight during the storm. Explosive avalanche testing produced slab avalanches up to size 2 on NE and NW aspects. With forecast snow and wind, we can expect to see a continued avalanche cycle.

Snowpack Summary

An additional 20cms accompanied by strong Southerly winds is forming new wind slabs and storm slabs on the upper snowpack. The upper 50-60cms of the snowpack is resting on a variety of older snow surfaces. These surfaces include previous cold, dry low density snow which may have had seen some faceting, old wind slabs, and crusts. Reports indicate it may be particularly reactive between 1700 and 1800m, although I would be concerned about this interface on all steep terrain right now. A rain crust lies buried approximately 30-50 cm below the snow surface at lower elevations (up to around 1800m). Reports indicate the bond at this interface is quite good, although the slick nature of the crust may still provide a sliding layer in some steeper locations. This may be a layer of concern with forecast wind, snow and rising freezing levels to come. Previous concerns about deeper persistent weak layers appear to have diminished. Snowpack depths at treeline are in the region of 260 cm.

Régions couvertes