Bulletin d’avalanche

Sea To Sky

Dec 6 – 7, 2012Avalanche Canada
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Archivé · expiré 14 years ago

Danger d’avalanche

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

The possibility of very large avalanches failing on the deeply buried crust is keeping the Alpine Danger elevated. I don't think we should trust big alpine slopes yet! Check out the forecast details for more info.

Problèmes avalancheux

  • Wind Slabs

    • Alpin
    • Limite forestière
    • Sous la limite forestière
    Probabilité
    Possible - Likely
    Taille
    2–5
    Stiff wind slabs are now covered with an additional 10-15 cms of new snow. These wind slabs may be triggered from weak shallow areas like exposed rocks or trees on the edge of slopes.

  • Deep Persistent Slabs

    • Alpin
    • Limite forestière
    • Sous la limite forestière
    Probabilité
    Unlikely - Possible
    Taille
    3–7
    An old facet/crust combination deep in the snowpack may wake up with heavy triggers, smaller avalanches stepping down, or triggering from thin-spots, particularly on slopes with smooth ground cover.

Avalanche Summary

Some natural cornice falls were reported up to size 2.0 after the recent very strong wind event. Some explosive controlled stiff wind slabs were reported up to size 1.5 from the Whistler area.

Confidence

Fair - Due to limited field observations on Friday

Weather Forecast

Overnight and Friday: Light to moderate precipitation overnight bringing 5-10 mm that should fall as snow above 800 metres elevation by late morning. Winds light westerly and alpine temperatures about -7.0Saturday:Light precipitation under cloudy skies, with light westerly winds and -10.0 in the alpine.Sunday: A Pacific frontal system is expected to move onto the coast during the day on Sunday. Expect a strong Southwest flow with moderate to heavy precipitation amounts.

Snowpack Summary

The recent very strong wind event has caused extensive wind scouring in the alpine and at treeline. Ski penetration is limited to about 10 cm above a stiff buried wind slab. Foot penetration may still be up to 70 cms as the wind slab is not able to carry the weight of a person without skis. The recent storm snow (up to about 130 cms) appears to be bridging above the early November weak layer, and we are not seeing deep releases down to the rain/ice crust. There is not much discussion about surface hoar that was buried last week, and we are not getting reports about test results on that layer. Professionals are concerned about the early November rain crust. If this deep persistent weak layer (DPWL) becomes reactive, the consequences will be very large destructive avalanches. The crust may be buried between 100-200 cms depending on the total depth of the snowpack in your area. The crust may be a bigger problem where it has a layer of facetted crystals above, rather than where it is like a laminated sandwich of crusts and facets. If that sounds too technical for you, then the take home is that this is not an easy problem to gauge when or where it might wake up.

Régions couvertes