Avalanche forecast

Northwest Coastal

Jan 1 – 2, 2013Avalanche Canada
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Avalanche danger

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

Avalanche problems

  • Wind Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Very Likely
    Size
    1–5
    Strong SW to SE winds have set up touchy new wind slabs in exposed lee terrain. The bond to the old snow surface is poor and comprises facets and/or surface hoar in some places.

  • Persistent Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Possible - Likely
    Size
    1–4

  • Loose Dry

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Possible - Likely
    Size
    1–3
    Loose dry avalanches will be easily triggered on steep terrain and in sheltered areas.

Confidence

Fair - Forecast snowfall amounts are uncertain

Weather Forecast

Wednesday: Moderate snowfall (up to 10cm) expected near the coast, tapering off rapidly with distance inland, meaning many areas likely to stay dry. Freezing levels around 1000 m. Strong ridgetop winds gusting in excess of 80 km/h from the SW.Thursday: Up to 10cm new snow, again focussed along the coast.  Freezing levels remaining around 1000 m. Ridgetop winds 60-80km/h.Friday: Light snowfall, Freezing levels dropping to around 500 m. Winds becoming moderate southerly.

Avalanche Summary

On Monday, avalanches up to size 2 were observed in the recent storm snow at all elevations. Although they appeared to only affect the top 10-20 cm of the snow surface, they were reported to be running far. Sluffing on steep terrain has also been reported.

Snowpack Summary

The recent new snow was warmer and denser in places than the existing snow on the ground, helping to create touchy storm slab conditions. The upper slab, while generally thin, was highly reactive in many places on Monday. Winds marked a significant shift from mostly light northerly to a period of strong south 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.

Regions covered