Avalanche forecast

Northwest Coastal

Jan 3 – 4, 2013Avalanche 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
    Likely
    Size
    2–6
    The new snow is expected to bond poorly with the old snow surface, which comprises buried facets and/or surface hoar in places. Strong or extreme SW to SE winds will continue to set up touchy new wind slabs in exposed lee terrain.

Confidence

Fair - Forecast snowfall amounts are uncertain

Weather Forecast

Friday: Flurries are possible, but should stay mostly dry. Freezing level around 300 m. Ridgetop winds initially 30-50 km/h, easing through the day. Saturday: Around 10 cm new snow is expected. Freezing level around 500 m. Winds moderate SW'ly. Sunday: Light precipitation. Freezing level around 200 m. Winds easing to light.

Avalanche Summary

Few observations, due to the bad weather. It is likely there are avalanches occurring in steep alpine terrain we have not heard about. On 31st December, there were reports of a few size 1 avalanches triggered on a layer of surface hoar layer buried 30 cm below the surface in the Shames backcountry.

Snowpack Summary

Recent storm snow amounts vary from 20 to 50cm and the bond between the new snow and the old is likely to be poor in many places. Winds have been strong southwesterly to southeasterly. These have set up touchy wind slabs in many exposed lee areas. There are two surface hoar layers in the upper snowpack. The upper one formed at the end of December and is buried approximately 30 cm below the surface. Professionals have reported easy, sudden planar compression test results on this layer and it has been reactive to skier-triggering. The lower one formed at the beginning of December and is buried approximately 90 cm below the surface. Hard, planar compression tests have been reported on this layer. Near the base of the snowpack, a crust/facet layer continues to give hard, sudden results to no results in snowpack tests. This weakness is unlikely to be triggered by a single person, but it remains possible with a very heavy load (e.g. cornice fall) or from a thin-spot trigger point.

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