Avalanche forecast

Northwest Coastal

Dec 30 – 31, 2011Avalanche Canada
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Avalanche danger

Sun
Mon
Alpine
3 · Considerable
Treeline
3 · Considerable
Below
3 · Considerable
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Avalanche problems

  • Wind Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Likely
    Size
    2–6
    Deep wind slabs exist in exposed lee and cross-loaded terrain in the alpine and at treeline. Large, sensitive cornices are also a current concern above lee slopes.

  • Persistent Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Possible
    Size
    1–6
    There is a possibility of highly destructive avalanches where the deeply buried mid-December crust/facet layer persists.

  • Storm Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Likely
    Size
    1–6
    Storm slabs could be triggered by the weight of a person, or by direct sunshine on Saturday.

Confidence

Fair - Timing or intensity of solar radiation is uncertain on Saturday

Weather Forecast

Saturday: A much drier day, with some light flurries possible. Snow beginning overnight with 5cm possible. Sunshine in some areas. Freezing level 500m. Moderate south-west winds.Sunday: 20cm snow during the day, with another 20cm overnight. Freezing level climbing to 1000m overnight. Moderate to strong southerlies.Monday: 5cm snow. Freezing level 1000m, lowering late on Monday to 500m.

Avalanche Summary

Wind slabs and cornice releases dominated recent avalanche observations. Highways avalanche control produced numerous Size 2-3.5 slab avalanches. The largest of these failed at ground, up to 4m deep.

Snowpack Summary

A relentless pummelling by snow, strong to extreme winds, and fluctuating freezing levels has added around 2m of new snow near Terrace and around 120cm near Stewart. Strong south to southwest winds have created hard and soft wind slabs on lee slopes. Large sensitive cornices also exist.Deeper in the snowpack, buried surface hoar and a crust-facet combo (which extends up to alpine elevations in the south and to 1000m in the north) remain a cause for concern, with the potential for deep, destructive avalanches. Recent observations suggest these layers may be gaining strength, however I wouldn't write them off just yet.

Regions covered