Bulletin d’avalanche

Kootenay Boundary

Dec 20 – 21, 2014Avalanche Canada
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Archivé · expiré 12 years ago

Danger d’avalanche

Mon
Tue
Alpin
4 · Fort
Limite forestière
3 · Marqué
Sous la limite
2 · Modéré
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Points saillants

A developing storm slab overlies very weak crystals. With more snow on the way, conservative terrain selection will be critical.

Problèmes avalancheux

  • Persistent Slabs

    • Alpin
    • Limite forestière
    • Sous la limite forestière
    Probabilité
    Unlikely - Possible
    Taille
    2–4
    Deeper layers have the potential to be re-activated during the storm, or from heavy triggers such as a cornice release.

  • Storm Slabs

    • Alpin
    • Limite forestière
    • Sous la limite forestière
    Probabilité
    Likely - Very Likely
    Taille
    1–4
    Steady snowfall, wind and rising temperatures are expected to create a punchy storm slab which overlies recently buried weak layers. Pay close attention to how much recent snowfall has accumulated in your area, and stick to conservative terrain.

Confidence

Fair - Timing, track, or intensity of incoming weather system is uncertain on Saturday

Weather Forecast

An intense frontal system will move across the province on Saturday night bringing moderate to locally heavy snowfall, extreme southwest winds and freezing levels to about 1300m. Scattered flurries are expected throughout Sunday. A dry ridge is expected to form on Monday bringing a mix of sun and cloud, moderate northwest winds and freezing levels at valley bottom. The weather pattern will shift again on Tuesday evening as another pacific system moves across the southern half of the province bringing moderate snowfall and rising freezing levels.

Avalanche Summary

On Wednesday, explosive testing produced small (size 1.5) avalanches on S to SE aspects at 2200 m in steep rocky terrain that were suspected to step down to the early November crust. Looking forward, natural storm slab activity is expected with weather forecast for Saturday night

Snowpack Summary

20-30 cm new snow has buried a prominent surface hoar layer above a thick rain crust that extends as high as 2400 m. As more snow falls, temperatures rise and winds increase on Saturday night, this developing storm slab will gain depth and cohesion adding to its destructive potential. The crust/surface hoar interface is expected to produce a very good sliding layer, and avalanches that run on this layer could travel far as a result. High elevation north aspect slopes do not have the rain crust, but on these slopes, facets or buried surface hoar from earlier in the month may be lurking under dense storm slabs. Recent snowpack tests at 2050 m in a NW aspect in Kootenay Pass produced moderate sudden results down 35 cm under the late-November crust and down 79 cm on facets above the early-November crust. There is a possibility that additional load from lots of new snow, or a large trigger such as a cornice release could still trigger a deeper slab on shady aspects at high elevations.

Régions couvertes