Avalanche forecast

Kootenay Boundary

Mar 16 – 17, 2012Avalanche Canada
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Avalanche danger

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

  • Wind Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Likely
    Size
    1–5
    Fresh wind slabs are forming on mostly north to east aspects in response to new snow and loading by SW winds. Old wind slabs are now buried but could enhance the size of potential releases on a variety of aspects in exposed areas.

  • Persistent Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Possible
    Size
    2–6
    The deep nature of the mid-February surface hoar layer makes potential avalanches triggered on this layer large and destructive.

  • Storm Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Likely
    Size
    1–5
    Heavy amounts of new snow are overloading buried weaknesses and could step down, producing large avalanches.

Confidence

Fair - Intensity of incoming weather is uncertain

Weather Forecast

Saturday: around 10 cm new snow is expected with a weak system moving in from the south. Winds starting out light, becoming moderate southeasterly in the afternoon. Freezing level around 1100 m. On Sunday and Monday: unstable air will continue to bring flurries, but sunny breaks are also possible, these becoming more prolonged as a ridge of high pressure builds on Monday. Light southwesterly winds. Freezing level around 900 m.

Avalanche Summary

On Friday, ski cutting produced avalanches down 25 cm in the recent storms snow. On Thursday, numerous large avalanches were noted on all aspects from 1600 to 2200m. In the Boundary region, avalanches were only noted in the storm snow. However, just to the north of the region, a size 4 avalanche as well as a couple of size 3 avalanches were observed, which stepped down to lower weak layers. On Wednesday, ski cutting and explosive testing produced avalanches up to size 2.5 on a variety of aspects. Just to the north of the region, a vehicle triggered a size 2.5 avalanche in the recent storm snow. 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

Rain fell to around 2000 m on Thursday afternoon and froze into a crust on all aspects below this elevation. Around 10 cm new snow now sits above the crust. The previous storm snow overlies a sun crust on southern aspects and maybe a spotty 2 - 6mm surface hoar on north and east aspects, down around 60 cm. Below that, the more significant 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. Cornices are growing and would act as a significant trigger for all the layers mentioned above if they drop.

Regions covered