Avalanche forecast

Kootenay Boundary

Mar 14 – 15, 2012Avalanche Canada
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Avalanche danger

Fri
Sat
Alpine
4 · High
Treeline
4 · High
Below
4 · High
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Highlights

Another significant storm is expected to roll through and maintain continued high danger for this region.

Avalanche problems

  • Wind Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Very Likely - Certain
    Size
    1–6
    Old wind slabs exist on a variety of aspects in exposed areas. Fresh wind slabs are forming on mostly north to east aspects in response to new snow and loading by SW winds.

  • Persistent Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Likely - Very Likely
    Size
    3–7
    The deep nature of the mid-February surface hoar layer makes potential avalanches triggered on this layer large and destructive. Regular and ongoing avalanche activity associated with this layer indicates it is very much still alive.

  • Storm Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Very Likely
    Size
    2–6
    If forecast heavy amounts of new snow come through, storm slabs may overload buried weaknesses & could even step down, producing large avalanches.

Confidence

Good

Weather Forecast

A significant storm is expected to bring around 10 cm new snow tonight and 30-40 cm on Thursday. Freezing levels are expected to peak at around 1700m on Thursday afternoon, meaning that some rain or sleet may fall at lower elevations during the storm. Ridgetop winds are expected to blow up to 70 km/h from the SW. On Friday, unsettled air that moves in behind the frontal system will continue to bring additional snow, but amounts should be lighter, around 10 cm. Winds should ease to moderate southwesterly. Freezing level will lower to around 1000m. On Saturday another storm looks as though it will affect the region, bringing further snow and strong winds.

Avalanche Summary

On Tuesday, several large (size 2.5) fracture lines in commonly skied areas at Kootenay Pass were observed following an intense wind event. On Monday, natural avalanches up to size 2 occurred in response to storm snow loading; ski-cutting to size 1.5 was also reported. This activity continues a very active period of avalanche activity that has been ongoing since early March.

Snowpack Summary

Recent storm slabs of around 20-40 cm overly a variety of surfaces including old wind slabs in exposed areas, a sun crust on southern aspects or even (spotty reports) a 2 - 6mm surface hoar on north and east aspects. Prior to that, recent most snow fell to around 1800m. The leap year SH is now down around 40 - 50 cm and is failing as a resistant planar shear in snowpack tests. The early February surface hoar is down 80 - 140cm, snowpack tests show moderate to hard forces generating sudden planar shears on this layer. Below the early February surface hoar layer, the snowpack is strong in most places.

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