Avalanche forecast

Northwest Coastal

Feb 15 – 16, 2016Avalanche Canada
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Avalanche danger

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

Stormy conditions on Tuesday are expected to form new wind slabs and storm slabs at higher elevations.  Use a conservative approach to travel and watch for changing conditions throughout the day as the storm progresses.

Avalanche problems

  • Storm Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Likely
    Size
    1–3
    New storm slabs are expected to develop in higher elevation terrain in response to loading from new snow and wind. Wind loaded areas will be the most immediate concern but a more widespread storm slab problem may develop in the deeper snowfall areas.

  • Deep Persistent Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Unlikely - Possible
    Size
    3–6
    Buried weak layers are still reactive in the snowpack, especially in the far north of region, and have the potential to produce very large avalanches. Thin spot triggering, cornice releases, and smaller avalanches all have the potential to step down.

Snowpack Summary

Up to 30cm of snow has accumulated over the past week and overlies a melt freeze crust which extends up to around 2000m elevation. This recent snow is reported to be bonding well to the crust. Moist snow was reported below 1100m on Sunday and wet snow below 800m. Recent wind has redistributed the surface snow at higher elevations forming soft wind slabs in leeward features. The early January surface hoar/facet layer is down 70-200 cm and remains a concern for commercial operations. This layer seems the most reactive in the north of the region and there have been several large avalanches reported in the past week releasing on this layer.

Confidence

Moderate - Timing, track, or intensity of incoming weather system is uncertain

Weather Forecast

Stormy conditions are expected Monday night through Wednesday morning. 15-25cm is expected between Monday night and Tuesday afternoon with strong southwest winds in the alpine and freezing levels around 800-1000m. Another 5-15cm is expected Tuesday overnight before a weak ridge of high pressure dries things out on Wednesday. A mix of sun and cloud is expected for Wednesday with freezing levels around 700m and light alpine wind. There is uncertainty for Thursday with one model showing a weak storm pulse and another showing dry conditions persisting.

Avalanche Summary

No new slab avalanches were reported on Saturday or Sunday. Ski cutting on Sunday produced only loose sluffing. On Friday, a skier triggered a size 1.5 wind slab on a northwest aspect at 1600m elevation. The slab was 10-20cm thick and was triggered on a thin, rocky, unsupported slope. Explosives also triggered several size 1.5 cornices on west aspects around 1500m elevation. As the storm progresses on Tuesday, wind slabs will likely form first and if enough snow accumulates, a more widespread storm slab problem could develop. In the far north, deeply buried persistent weak layers may still be reactive to large triggers such as a cornice fall or a smaller avalanche stepping down.

Regions covered