Bulletin d’avalanche

Kootenay Boundary

Jan 27 – 28, 2015Avalanche Canada
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Archivé · expiré 12 years ago

Danger d’avalanche

Thu
Fri
Alpin
3 · Marqué
Limite forestière
3 · Marqué
Sous la limite
2 · Modéré
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Points saillants

The cooling has started, but it may take a couple of days to recover from the very warm air and high freezing levels.

Problèmes avalancheux

  • Persistent Slabs

    • Alpin
    • Limite forestière
    • Sous la limite forestière
    Probabilité
    Likely
    Taille
    1–4
    Continued warming from high freezing levels and strong solar radiation may result in natural avalanches releasing on the buried persistent weak layer on Southerly aspects. Avalanches may be human triggered on all aspects.

  • Loose Wet

    • Alpin
    • Limite forestière
    • Sous la limite forestière
    Probabilité
    Likely
    Taille
    1–4
    Moist or wet loose snow is expected to continue to release from light additional loads, or from strong solar radiation on Southerly aspects. 

  • Deep Persistent Slabs

    • Alpin
    • Limite forestière
    • Sous la limite forestière
    Probabilité
    Possible
    Taille
    3–6
    Very warm temperatures and high freezing levels may result in deeply buried weak layers reacting to large loads like cornice falls or from light loads in thin snowpack areas.

Confidence

Fair - Timing or intensity of solar radiation is uncertain

Weather Forecast

The freezing level is expected to drop overnight down slightly below 1000 metres and then rise again on Wednesday up to 1500 metres. Expect valley cloud in most areas with clear skies above 1500 metres combined with light winds on Wednesday. The freezing level should drop down to valley bottoms by Thursday morning and then rise up to about 1000 metres during the day. Valley cloud may persist with clear skies and light winds above. Southwest winds should develop on Friday as cloud moves into the region ahead of the next Pacific front.

Avalanche Summary

On Monday there were several size 2.0-2.5 loose wet and wet slab avalanches released with explosives at Kootenay Pass, and a size 3.0 natural avalanche in the backcountry near Whitewater ski resort on a Southeast aspect with a very wide propagation that probably released on the mid-January persistent weak layer during a period of strong solar radiation. Moist or wet loose snow avalanches have been reported from several areas up to size 2.0 over the past few days during the warming event. On Saturday a skier triggered a size 2 persistent slab which failed on the mid-December layer. This was a surprising result because it was on a well-supported, concave terrain feature (which had also been heavily skied).

Snowpack Summary

The recent snow overlies various surfaces including surface hoar, a thin crust, or a settled slab. Warm temperatures are affecting the surface layers and turning them moist or wet. Continued warming has increased the likelihood of triggering the persistent weak layer of mid-Jan surface hoar layer which is down about 20-60 cm. These large, well-preserved surface hoar crystals sit on a thin crust up to about 1900m on north aspects and all the way to ridgeline on south aspects. A deeper crust/surface hoar combo buried in mid-December is typically down 80-120cm and has produced some large avalanches recently.

Régions couvertes