Avalanche forecast

Kootenay Boundary

Feb 9 – 10, 2015Avalanche Canada
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Avalanche danger

Wed
Thu
Alpine
4 · High
Treeline
3 · Considerable
Below
3 · Considerable
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Highlights

Recent heavy snowfall has over-loaded weak layers, and very large avalanches are still a concern. Conservative terrain selection remains critical.

Avalanche problems

  • Persistent Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Possible
    Size
    3–6
    Buried persistent weak layers in the mid snowpack have been over-loaded by the new storm snow. Very large and destructive avalanches have occurred under light loads, and conservative terrain selection remains critical.

  • Storm Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Possible - Likely
    Size
    1–5
    At higher elevations deep and destructive storm slabs overlie a weak crust/ surface hoar interface. Very large avalanches are still possible under light loads, especially with forecast warming and possible solar radiation.

  • Loose Wet

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Possible - Likely
    Size
    1–3
    Pushy loose wet and wet slab avalanches remain a concern at lower elevations where rain has saturated the snowpack. Pay close attention to daytime temperatures, and whether snow surfaces are moist or refrozen.

Confidence

Fair - Timing or intensity of solar radiation is uncertain on Tuesday

Weather Forecast

Remnant moisture from the pineapple express will bring light precipitation to the region on Tuesday morning. By the end of the day, a warm dry ridge of high pressure will develop bringing progressively warmer temperatures and clearing throughout the forecast period. Tuesday: Light snowfall and overcast skies / Light northwest winds / Freezing levels at 1800m Wednesday: Mix of sun and cloud / Moderate southwest winds / Freezing level at 1800m Thursday: Mix of sun and cloud / Moderate southwest winds / Freezing level climbing to 2700m

Avalanche Summary

Over the last few days there was a widespread avalanche cycle to size 3.5. Most of the avalanches were storm slabs which formed in response to new snow and wind, although many avalanches stepped down to the late and mid January surface hoar/crust layers. On Sunday, many of these avalanches were still failing naturally or with remote triggers. Looking forward, very large persistent slab avalanches remain a concern, especially with forecast warm temperatures and potential for solar radiation.At lower elevations where the snowpack is rain-soaked, there is potential for ongoing loose wet or wet slab avalanches. Although if snow surfaces refreeze and form a strong crust, this will be unlikely.

Snowpack Summary

Heavy precipitation over the past few days has resulted in deep and dense storm slabs above about 1800m. At lower elevations heavy rain has saturated the snowpack which, depending on the temperature, will now appear wet or refrozen. Moderate to strong southwest winds have shifted the new snow accumulations into much deeper deposits in exposed lee terrain. Below the recent storm snow you'll find a hard melt freeze crust which exists up to 100cm below the surface. This crust, which formed at the end of January, may have weak overlying surface hoar and is still reported to be very reactive in some areas. Deeper in the snowpack the mid-January surface hoar remains a concern. It can be found down 80-140 cm across the region. In some locations it has reportedly gained quite a bit of strength, but elsewhere it is still producing very large avalanches under the weight of the recent snow load.The mid-December surface hoar layer is now 100 to 170cm below the surface and has become unlikely to fail.

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