Avalanche forecast

South Columbia

Feb 11 – 12, 2013Avalanche Canada
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Avalanche danger

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

Avalanche problems

  • Wind Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Possible - Likely
    Size
    1–4
    Wind slabs exist on lee slopes and behind terrain features like ribs and ridges. Recent changing winds may load unsuspecting aspects and catch you by surprise.

  • Persistent Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Possible
    Size
    2–5
    Persistent slabs are 40-80 cm thick and continue to be reactive above variable sliding surfaces comprising of surface hoar, crusts and facets. They may be triggered by the weight of a skier or a machine.

Confidence

Fair - Intensity of incoming weather is uncertain

Weather Forecast

Tuesday: A frontal system approaches the coast and moves across the province. Flurries are expected during the day (2-3 cm) and moderate snow in the evening and overnight (~10 cm). Winds increase to strong from the southwest later in the afternoon. The freezing level is around 1200 m. Wednesday: Possible flurries early then a mix of sun and cloud. The freezing level drops to 500 m. Winds are light from the northwest. Thursday: A mix of sun and cloud. The freezing level is near valley bottom. Winds are light from the west.

Avalanche Summary

Natural avalanche activity loose and slab avalanche activity up to size 2.5 continues through the region. Rider triggered avalanches are ongoing and we have continued to receive reports of rider triggered slab avalanches up to size 2. Most of these cases still involving the persistent weak layers below the surface. There was one report of a size 3.5 explosive triggered avalanche on Sunday. This was triggered with large explosives in very steep terrain and resulted in a crown that was around 40 cm deep and propagated at least 300 m wide.

Snowpack Summary

The snow surface consists of new wind slab in exposed alpine terrain, a sun crust on solar aspects, and surface hoar and/or facets on shady slopes. Below this 20-40 cm of settled storms snow sits on a surface hoar and sun crust layer that developed at the beginning of February. This layer continues to be reactive to rider triggers. Deeper down (between 40-80 cm) sits an old sun crust and well preserved surface hoar that was buried on January 23rd. This persistent slab has been reactive over the past few days, especially from solar aspects and at treeline and below treeline over steeper convex slopes. During recent snowpack testing this layer has shown  moderate compression results with sudden planar to resistent planar characteristics. This layer is getting stronger over time and less likely to trigger, but if triggered it will still produce a significant avalanche. The mid-pack is generally well settled and strong.

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