Avalanche forecast

Northwest Inland

Dec 13 – 14, 2012Avalanche Canada
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Avalanche danger

Sat
Sun
Alpine
3 · Considerable
Treeline
3 · Considerable
Below
2 · Moderate
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Highlights

Avalanche problems

  • Storm Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Possible - Likely
    Size
    1–5
    Storm slabs are likely to be encountered on many slopes. Be alert for new and buried wind slabs behind ridges and ribs. Storm/wind slabs could step down to trigger a persistent weakness, creating a very large avalanche.

  • Deep Persistent Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Possible
    Size
    2–6
    A deeply buried facet/crust weakness exists. Very large and destructive avalanches may be triggered from thin snowpack areas or by heavy loads such as a storm slab stepping down, or a snowmobile spinning its tracks.

Confidence

Fair - Timing of incoming weather is uncertain for the entire period

Weather Forecast

Friday: Strong W to SW winds. Alpine temp -5. Light snow starting late in the day.Saturday: Strong to gale SW winds. Alpine temp -6. Moderate to heavy snow. Sunday: Light SE winds. Alpine temp -13. Light snow.

Avalanche Summary

On Wednesday, a snowmobile triggered a hard wind slab at the Sinclair snowmobiling area. It failed on the November crust/facet layer 30 cm above the ground. Evidence of a recent natural cycle was also reported. This deep crust/facet layer has been the failure plane for a number of large avalanches further to the west and was suspected to have failed at the Hankin-Evelyn area last weekend. Unfortunately, this weakness is unlikely to heal very quickly, so further deep avalanches are possible, especially as snow and wind-loading continue to stress the snowpack over the next few days.

Snowpack Summary

Storm snow instabilities are likely to continue developing over the next few days as variable new snow layers build up. Spotty surface hoar is also buried in the upper snowpack, particularly in sheltered treeline areas. New and buried wind slabs are widespread and exist on a variety of alpine and exposed treeline slopes due to variable winds. Of key concern is a November facet/crust layer which can be found near the base of the snowpack. This layer, which is widespread, can be triggered from thin-spot trigger points, or with a heavy load, such as storm slabs stepping down, cornice fall or a snowmobile. It has the potential for very large, destructive avalanches and demands respect. A rain crust is buried in the upper snowpack at low elevations. In general the snowpack is highly variable in depth due to windy conditions this season.

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