Bulletin d’avalanche

Sea To Sky

Dec 7 – 8, 2011Avalanche Canada
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Archivé · expiré 15 years ago

Danger d’avalanche

Fri
Sat
Alpin
2 · Modéré
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
    Possible
    Taille
    1–3
    Weak wind slabs may still be lurking below ridge crests, behind terrain features, and in cross-loaded gullies.

  • Deep Persistent Slabs

    • Alpin
    • Limite forestière
    • Sous la limite forestière
    Probabilité
    Unlikely - Possible
    Taille
    2–7
    The right trigger (big air onto steep unsupported slope, sled track trenching deep in a thin area) could have disastrous consequences. The greatest concern is in the Whistler area on slopes with variable snowpack depths above 1900m.

Confidence

Fair - Due to limited field observationsfor the entire period

Weather Forecast

The current weather pattern is expected to hold Thursday and Friday with a temperature inversion bringing above freezing temperatures to alpine elevations. The associated valley cloud is expected to blow out Wednesday afternoon with moderate northerly outflow winds, resulting in sunny skies at all elevations. A week frontal system is expected for Saturday with increasing cloud and a chance of light precipitation and moderate westerly winds.

Avalanche Summary

Avalanche activity has tapered off throughout the week. Although the likelihood of triggering deep persistent slab avalanches is low, the potential consequences are still very high.

Snowpack Summary

Surface hoar is growing, surface snow is faceting, and pockets of weak wind slab may still be lingering on various aspects in the alpine.Warm temperatures and sun-exposure likely resulted in a surface crust on steep south aspects. Last weekends rain crust is down 20-40cm and extends up to treeline elevations. Basal depth hoar with an associated crust is prevalent in thin snowpack areas, and especially problematic where it is overlying summer firn. Above that, and down 1-2m, are two more crusts mixed with facets, depth hoar, and surface hoar. Recent compression tests in a shallow snowpack area produced moderate sudden collapse results on this deep persistent weakness. Time has allowed the overlying snow to gain strength making it less likely to trigger the deeper weaknesses, but if you do hit the sweet spot, such as a shallow area, the resulting avalanche could have very serious consequences.

Régions couvertes