Avalanche forecast

Kootenay Boundary

Dec 20 – 21, 2018Avalanche Canada
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Avalanche danger

Sat
Sun
Alpine
3 · Considerable
Treeline
3 · Considerable
Below
3 · Considerable
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Highlights

Clearing skies may entice us to bigger slopes, but it is a good time to remain conservative; recent storm slabs overly a touchy weak layer.

Avalanche problems

  • Persistent Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Possible
    Size
    1.5–3
    A weak layer buried around 50 to 100 cm is the primary concern. This weak layer has recently produced large avalanches. Shallower storm slab avalanches could step down to this layer and produce larger avalanches.

  • Storm Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Possible - Likely
    Size
    1–2
    The storm snow from Thursday may not bond well to previous surfaces. Expect to find the deepest slabs in lee terrain features, as strong southerly winds accompanied the storm.

Confidence

High.

Weather Forecast

THURSDAY NIGHT: Cloudy with light snowfall, freezing level dropping from 1300m to below valley bottom. FRIDAY: Clearing over the day, moderate to strong northwest winds, alpine temperature -11°c, freezing level below valley bottom. SATURDAY: Partly cloudy, moderate southwest winds, alpine temperature -9°c, freezing level below valley bottom. SUNDAY: Cloudy with light snowfall, accumulation 5 to 10cm, moderate southwest winds, alpine temperature -5°c, freezing level below valley bottom.

Avalanche Summary

Large (size 2 to 3) slab avalanches were triggered naturally, by skiers, and explosives on Tuesday and Wednesday. The avalanches were generally 50 to 70cm deep and either within the storm snow or on the weak layer described in the snowpack discussion.

Snowpack Summary

Around 50 to 100cm of recent storm snow overlies a rain crust and a weak layer of feathery surface hoar and sugary facets. Avalanche activity, remote triggering, and snowpack test results tell us that it is a critical layer. It is best to travel extremely cautiously with this layer in the snowpack.The lower snowpack is well-settled.

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