Avalanche forecast

Kootenay Boundary

Feb 21 – 22, 2016Avalanche Canada
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Avalanche danger

Tue
Wed
Alpine
3 · Considerable
Treeline
3 · Considerable
Below
3 · Considerable
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Highlights

Large amounts of recent storm snow may push the hazard higher than forecast. Choose your riding terrain carefully and be conservative with route selection.

Avalanche problems

  • Wind Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Likely
    Size
    1–3
    Large amounts of new snow in the past week, combined with moderate to strong south west winds have built wind slabs in lee terrain at tree line and above. New snow may sluff in steep terrain and trigger deeper instabilities.

  • Cornices

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Possible
    Size
    1–4
    Cornice are growing large and menacing. With warming temperatures they will become more fragile. A cornice failure could produce enough mass to trigger deeply buried instabilities and create a large, destructive avalanche.

  • Persistent Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Possible
    Size
    2–5
    A crust and surface hoar layer now lies buried up to 130cm below the surface in many parts of the region, it may not be found on every slope, but an avalanche at this interface could be quite large. Keep this layer on the radar for future reference.

Confidence

High - Due to the number and quality of field observations

Weather Forecast

A Pacific frontal system is forecast to pass through the region later today with light precipitation overnight and through Monday.Upper elevations may see 5 cm of new snow. There should be a bit of a break Monday evening, then a weak system on Tuesday will bring clouds, but very little precipitation is forecast. A ridge of high pressure will rebuild over the province bringing clear skies and no precipitation through the remainder of the week. Freezing levels will rise to 1000 metres during the day, then drop to valley bottom overnight.

Avalanche Summary

Numerous skier controlled, explosive controlled and naturally triggered storm slab avalanches were reported yesterday and ranged up to size 3. Early reports today list 3 skier accidentals in the region. These most likely failed in response to heavy storm and wind loading throughout the past week.. A number of these avalanches released on the February crust interface mentioned in the Snowpack Discussion section. The combination of wind, rapid loading, warm temperatures and increased radiation on solar aspects makes for a perfect recipe for large avalanches.

Snowpack Summary

Parts of the region received another 10 to 20cm of snow overnight. Light winds that accompanied the recent snowfall may transport the new snow into lee terrain and hide previously wind loaded pockets. 90-120 cm below the surface a hard melt-freeze crust exists that formed during the 2nd week of February. This crust is quite widespread and may co-exist with weak surface hoar or facets. This variably reactive interface is a critical layer to watch in the region and has caught a few people by surprise in recent days. Buried surface hoar layers exist in the top 120 cm in drier areas on the west side of the region near Rossland. In other areas a January surface hoar layer can be found 100-190 cm deep and poses a low probability/ high consequence threat. It should remain on your radar, especially in thin snowpack areas and during periods of significant warming or rapid loading.

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