Avalanche forecast

Kootenay Boundary

Feb 13 – 14, 2015Avalanche Canada
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Avalanche danger

Sun
Mon
Alpine
3 · Considerable
Treeline
2 · Moderate
Below
1 · Low
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Highlights

A Special Public Avalanche Warning is in effect for this region. The only worthwhile riding is likely on the least trustworthy slopes. Be circumspect on large  steep alpine slopes.

Avalanche problems

  • Cornices

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Possible
    Size
    1–3
    Cornices will likely become unstable with fluctuating temperatures. Not only are they a hazard in themselves, but they are also large triggers for deep slab avalanches on the slope below.

  • Storm Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Possible
    Size
    1–5
    Warm temperatures and sunshine could destabilize the recent snow resulting in isolated slab activity and loose wet sluffs, particulary on steep sun-exposed slopes.

  • Deep Persistent Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Possible
    Size
    3–6
    Deep persistent weaknesses recently woke up with the warm temperatures and should be treated with suspicion until after things freeze up again. Although likely to need a large trigger, the potential consequences are dire.

Confidence

Good

Weather Forecast

Saturday: Cloudy with possible light snow. The freezing level lowers to around 1800-2000 m. Winds are generally light from the W-NW. Sunday: Cloudy with light snow and occasional sunny breaks. The freezing level is around 1400-1500 m. Monday: Mainly sunny and dry with light winds and freezing levels around 1500 m.

Avalanche Summary

Reports from Thursday include isolated large explosive triggered persistent slab avalanches failing on the mid-January surface hoar on northeast facing treeline and alpine slopes. These slabs were 80-150 cm thick with some wind-loaded pockets as deep as 2 m. One avalanche was described as 'sluggish', but highly destructive, taking out mature timber on the way down.

Snowpack Summary

Recent warm temperatures have softened the upper snowpack, reawakening deep persistent weaknesses in isolated areas. As temperatures continue to fluctuate and stress the snowpack, expect an increased likelihood of triggering large destructive avalanches in isolated areas (e.g. thin spots) with heavy triggers (e.g. cornice falls, stuck sleds spinning tracks, or groups of people). Approximately 65-100 cm of recent storm snow is bonding well to a crust buried at the beginning of February; however, this bond is much weaker where surface hoar overlies the crust. Below that, recent snowpack tests gave moderate to hard but sudden collapse results on the mid-January surface hoar where it was found down 70-82 cm on a northeast facing treeline slope. This persistent weakness has been found as deep as 110 cm, or deeper on wind-loaded slopes. The mid-December crust/facet/surface hoar weakness may be persisting in the mid to lower snowpack at higher elevations.

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