Bulletin d’avalanche

Sea To Sky

Mar 15 – 16, 2012Avalanche Canada
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Archivé · expiré 15 years ago

Danger d’avalanche

Sat
Sun
Alpin
4 · Fort
Limite forestière
4 · Fort
Sous la limite
3 · Marqué
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Problèmes avalancheux

  • Wind Slabs

    • Alpin
    • Limite forestière
    • Sous la limite forestière
    Probabilité
    Likely - Very Likely
    Taille
    1–6
    Wind slabs lurk below ridges, behind terrain features and in gullies. Strong winds may create slabs unusually low on the slope or in openings below treeline.

  • Persistent Slabs

    • Alpin
    • Limite forestière
    • Sous la limite forestière
    Probabilité
    Possible
    Taille
    4–8
    Persistent weaknesses, now about 1.5m deep, demand respect. The potential for remote triggering, step down avalanches, and wide propagations makes this persistent slab problem particularly intimidating and tricky to manage.

  • Storm Slabs

    • Alpin
    • Limite forestière
    • Sous la limite forestière
    Probabilité
    Likely - Very Likely
    Taille
    1–6
    Storm slabs are building ever deeper with successive weather systems and are failing under their own weight. They are also overloading persistent weak layers.

Confidence

Fair - Timing or intensity of solar radiation is uncertain

Weather Forecast

An unstable air mass will bring mainly cloudy skies and light snow amounts through the weekend, with freezing levels remaining at or near the valley bottom. If the sun shines through, solar radiation will be intense. Friday: Snow amounts 5-10 cm. Ridgetop winds moderate from the SW. Alpine temperatures -6. Freezing levels near 800 m. Saturday: Snow amounts near 5-10 cm. Cloudy skies. Ridgetop winds light from the SW. Freezing levels at valley bottom. Sunday: Mainly dry, cold conditions. Broken skies in the morning, sunny skies in the afternoon. Solar radiation may be intense. Freezing levels valley bottom.

Avalanche Summary

On Tuesday a natural avalanche cycle occurred up to size 3 on N-NE aspects. Cornices reached their threshold and triggered slopes up to size 2.5 below. On Monday, a skier was partially buried and two others escaped a size 2 slab on an east aspect at 1500m, which failed on a crust. Natural and skier-remote triggered avalanches to size 3 were also observed on a variety of aspects and elevations, some failing on the mid-February weakness. Crowns were up to 150cm deep. Every day of the last week, avalanches have been triggered either naturally, remotely or accidentally by backcountry travelers. Unsettled weather conditions continue. It may take several days for all this new storm snow to settle out. If the sun shines through in your local mountains; expect strong solar radiation, snowpack deterioration, and elevated avalanche danger.

Snowpack Summary

Stormy conditions continue! Over 1100-180 cm storm snow has fallen, accompanied by strong SW winds. Storm slabs and wind slabs continue to build. Cornices are large, some reaching threshold and triggering the slopes below. For the most part, the new storm snow is right side up (lower density snow on top) and easy to moderate shears exist within the upper meter. The additional weight of new storm and wind slabs may step down and trigger a deep weakness, formed in mid-February. Recent test results on this layer produced hard sudden planar results down 120cm in the snowpack (DTH24 SP dwn 120cm on FC/RG 0.5). Very large avalanches are possible, which could be remote-triggered, triggered mid-slope, and/or propagate into low-angled terrain.

Régions couvertes