Avalanche forecast

South Rockies

Dec 19 – 20, 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 - Likely
    Size
    1–3
    Shifting winds have set up wind slabs on a variety of aspects, particularly north through southeast. Cross-loading is also possible on open slopes generally oriented parallel to the wind, which contain features and gullies to catch wind-drifted snow.

Confidence

Good - -1

Weather Forecast

Tuesday: 3-5 cm new snow expected with strong NW ridgetop winds. Alpine temperatures falling rapidly to around -15C by the afternoon.Wednesday: Lingering flurries possible. Moderate northerly ridgetop winds. Alpine temperatures around -18C.Thursday: Dry and bright. Ridgetop Winds becoming westerly. Remaining cold, but a mild inversion should elevate alpine temperatures to around -10C.

Avalanche Summary

We have had reports of shallow slab avalanches affecting the top 20 cm of the snowpack, running on the mid-December surface hoar layer. Although these shallow slides (to size 1.5) do not have much mass, they were reported as running "fast and far". They were reported from the Harvey Pass area at 1800-2000m on a north aspect.

Snowpack Summary

A significant wind event on Saturday redistributed snow, scouring west-facing slopes and depositing highly variable wind slabs on east-facing slopes. Current winds are from the northwest, so expect fresh wind slabs to develop on southeast facing slopes. A buried layer of surface hoar lies approximately 20 cm below the snow surface. Reports indicate this layer was blown around before it was buried and can only be found in isolated, sheltered locations. A well settled mid pack bridges over the basal weaknesses at the ground. The crust/facet combo still exists at the ground. This layer was responsible for some large releases earlier on in the season. However, there hasn't been any activity on this layer since early December and confidence is growing that it is gaining strength.

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