Avalanche forecast

Sea To Sky

Dec 5 – 6, 2011Avalanche Canada
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Avalanche danger

Wed
Thu
Alpine
2 · Moderate
Treeline
2 · Moderate
Below
1 · Low
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Avalanche problems

  • Wind Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Possible
    Size
    1–2
    Gusty winds have redistributed surface snow creating pockets of wind slab on a variety of aspects.

  • Deep Persistent Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Unlikely - Possible
    Size
    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 with rocky slopes with variable snowpack depths above 1900m.

Confidence

Good - Due to limited field observationsfor the entire period

Weather Forecast

Tuesday: Increasing clouds throughout the day, but no precipitation is expected until the evening. The freezing levels should drop to around 1900m as the temperature inversion weakens. Alpine winds are expected to remain light. Wednesday: Light flurries possible in the morning, then clearing throughout the day. Light northerly winds with freezing levels around 1200m. Clear, light wind , and freezing levels around 1900m.

Avalanche Summary

Avalanche activity has tapered off throughout the week. Although the likelihood of triggering avalanches is lower, the potential consequences are still very high.Likelihood of avalanches may increase on steeper, sun exposed slopes with forecast rising temperatures.

Snowpack Summary

Surface hoar is growing, surface snow is faceting, and pockets of weak wind slab may still be lingering on various aspects at and above treeline. Warm alpine temperatures and sun-exposure are creating wet surface snow in the afternoon, especially on south facing slopes, which is subsequently freezing into a crust overnight. 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. 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.

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