Bulletin d’avalanche

Kootenay Boundary

Jan 24, 2017Avalanche Canada
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Archivé · expiré 10 years ago

Danger d’avalanche

Tue
Wed
Alpin
3 · Marqué
Limite forestière
2 · Modéré
Sous la limite
1 · Faible
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Points saillants

Wind slabs have combined with a persistent slab to form complex avalanche hazard in our region. Low snow areas are especially concerning.

Problèmes avalancheux

  • Wind Slabs

    • Alpin
    • Limite forestière
    • Sous la limite forestière
    Probabilité
    Possible - Likely
    Taille
    1–2
    Watch out for touchy pockets of wind slab lingering on exposed northerly features near ridge crests, and also in cross-loaded southeast gullies at treeline.

  • Persistent Slabs

    • Alpin
    • Limite forestière
    • Sous la limite forestière
    Probabilité
    Possible
    Taille
    2–3
    Several different persistent weak layers are buried 60-150 cm deep and have proven reactive to human triggering. Conservative terrain use is essential in managing the problem, especially in low snow areas such as the southwest portion of the region.

Confidence

Moderate -

Weather Forecast

Tuesday: Mainly cloudy with possible isolated flurries bringing a trace of new snow. Winds light from the northwest. Freezing level to 800 metres with alpine temperatures of -8. Wednesday: Mainly cloudy with isolated flurries and a trace of new snow. Winds light from the northwest. Freezing level to 600 metres and alpine temperatures around -10. Thursday: Mainly cloudy with isolated flurries and a trace of new snow. Winds light from the northwest. Freezing levels around 700 metres with alpine temperatures to -9.

Avalanche Summary

Preliminary information regarding the backcountry skier fatality on Saturday is that it occurred on a S/SE facing aspect near 2050m in a cross-loaded feature. Reports from Sunday include several natural Size 1-1.5 wind slab avalanches that occurred on a northwest aspect after a bout of rapid wind loading over the morning.We also had a great MIN report of a cornice-triggered Size 2 on Friday near Cabin Peak in the Bonnington range. The initial failure was in the storm slab on a southeast aspect near 2000m but more significantly was observed stepping down to trigger a weak layer deeper in the snowpack.

Snowpack Summary

A complex and tricky snowpack exists in the Kootenay Boundary region. By Sunday morning another 3-12 cm added to the previous 35-55 cm of fresh snow from last week (which was accompanied by moderate to strong southerly winds). This resulted in touchy storm and wind slabs bonding poorly to the previous snow surface that includes facets and large surface hoar on sheltered slopes and/or a sun crust on steep sun-exposed aspects. The Jan 17th surface hoar layer continues to give easy sudden results in snowpack tests (down anywhere from 30 to 60cms depending on location). In some areas of the Rossland range, the mid-November rain crust / facet layer is now likely down 60-100 cm and has become reactive with continued loading and warming. In thin rocky areas, particularly in the Rossland range, recent reports include easy sudden collapse snowpack test results on facets down 120-150 cm near the ground. This deep persistent weakness may also become reactive with continued loading and warming.

Régions couvertes