Avalanche forecast

Sea To Sky

Mar 20 – 21, 2012Avalanche Canada
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Avalanche danger

Thu
Fri
Alpine
3 · Considerable
Treeline
3 · Considerable
Below
2 · Moderate
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Avalanche problems

  • Wind Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Likely
    Size
    1–6
    Wind slabs lurk below ridges, behind terrain features and in gullies. They may be buried by new snow, making them hard to spot. Large cornices have formed, and threaten slopes below.

  • Storm Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Possible - Likely
    Size
    1–6
    Variable new and old storm slabs will be easiest to trigger on steep or convex terrain.

  • Deep Persistent Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Unlikely - Possible
    Size
    4–8
    Persistent weaknesses still have the potential to create very large, destructive avalanches if triggered. Possible triggering mechanisms include a person/sled on a thin snowpack spot, cornice fall, or step-down avalanche.

Confidence

Fair - Timing, track, or intensity of incoming weather is uncertain

Weather Forecast

Wednesday: Convective snow showers. Moderate south-westerly winds, decreasing through the day. Freezing level around 700m.Thursday: Light snow. Light, south-easterly winds. Freezing level around 500m. Friday: Cloudy with flurries. Freezing level remaining near 500m.

Avalanche Summary

Last week was very active with natural avalanche activity up to size 3.5 and several rider involvements and close calls. Some avalanches failed on the mid-February persistent weakness. On Monday, a skier triggered a buried wind slab on a convex roll 30-40cm deep on a north-east aspect. Some natural activity was also observed on steep solar aspects. On Sunday, a skier triggered a size 1.5 from a north-east aspect, in steep rocky terrain. Avalanches were also triggered naturally and by explosives in steep, rocky terrain to size 2. A size 3 slab was observed on a north-west aspect in the Musical Bumps area, near Whistler, suspected to have failed on Sunday. The trigger is unknown.

Snowpack Summary

Snow and wind created fresh wind slabs and storm slabs on Tuesday. Heavy snow which fell last week is slowly settling, but variable storm snow weaknesses and buried crusts mean a deep storm slab release is still possible. Cornices are large and threaten slopes below. A persistent weakness, formed in mid-February, continues to produce hard, sudden planar results in snowpack tests. The likelihood of triggering this layer has gone down, but very large avalanches remain possible, which could be triggered by a shallower avalanche or cornice fall. The average snowpack depth at treeline is 350cm.

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