Avalanche forecast

Northwest Coastal

Dec 16 – 17, 2012Avalanche Canada
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Avalanche danger

Tue
Wed
Alpine
3 · Considerable
Treeline
2 · Moderate
Below
2 · Moderate
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Highlights

Avalanche problems

  • Storm Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Possible
    Size
    1–5
    Storm snow instabilities are possible on steeper slopes where new snow accumulations are greater than 30 cm. New windslabs are likely behind ridges, ribs, or similar terrain breaks.

  • Deep Persistent Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Unlikely
    Size
    3–7
    Deeply buried weaknesses exist. Dropping cornices or smalller surface slides could step down.

Confidence

Fair - Due to limited field observations

Weather Forecast

Synopsis: On Monday & Tuesday the region will see a cool unstable onshore flow with light SW winds, light snowfall with no significant accumulation, and freezing level near valley bottom. The next system is not arriving until sometime Wednesday when a Gulf of Alaska Low starts sliding south off the coast.

Avalanche Summary

In areas with deeper storm snow accumulations (for example near Stewart) natural avalanches to size 2.5 were reported; otherwise no new naturals reported but visibility was limited.

Snowpack Summary

Storm snow accumulations in the north and near the coast (for example the mountains near Stewart) are as high as 65 cm; away from the coast there was much less. For example near Shames it was closer to 20 cm of storm snow but the total snowpack depth only added 5 cm due to settling. The upper snowpack should be mostly settling powder depending on elevation. I expect wind slabs or wind affected snow in higher elevation exposed areas. Deeper in the snowpack professionals continue to monitor a crust down near the ground. It seems this problem is confined to  alpine areas and likely needs a large trigger and / or a shallow snow pack feature to trigger.

Regions covered