Bulletin d’avalanche

South Columbia

Jan 26 – 27, 2016Avalanche Canada
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Archivé · expiré 11 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

Strong winds and rising freezing levels are pushing the danger ratings up. Conservative terrain choices without overhead hazards are recommended at this time.

Problèmes avalancheux

  • Wind Slabs

    • Alpin
    • Limite forestière
    • Sous la limite forestière
    Probabilité
    Likely
    Taille
    1–3
    New wind slabs are expected to develop due to forecast new snow and southwest wind. Wind slabs in motion may trigger the deeper persistent weak layer resulting in large avalanches.

  • Persistent Slabs

    • Alpin
    • Limite forestière
    • Sous la limite forestière
    Probabilité
    Possible - Likely
    Taille
    2–5
    Loading from wind, snow, and rain, may increase the likelihood of triggering the slab above the buried persistent weak layer. Remote triggering continues to be a concern.

Confidence

Moderate - Freezing levels are uncertain

Weather Forecast

Strong southwest winds overnight with periods of snow and freezing levels around 1000 metres. Cloudy with flurries or light snow on Wednesday combined with moderate southwest winds and freezing levels rising up to about 2200 metres. Freezing levels remaining high overnight as heavy precipitation moves into the region on Thursday. There is some uncertainty with the freezing level, check back tomorrow for an update on the rain/snow line. Cooler air is expected on Friday with light winds and snow down to valley bottoms.

Avalanche Summary

Natural avalanches up to size 3.0 were reported on Monday in the southern monashees, and up to size 2.5 in the southern selkirks. Numerous slab avalanches up to size 3 were reported over the weekend. Most of the natural avalanche activity occurred on Friday and Saturday but several were still reported on Sunday. A large number of skier triggered avalanches were also reported. Many of these failed at treeline and below on buried surface hoar down 30-60 cm. Many of these were triggered remotely, highlighting the volatility of the persistent slab. An increasing number of wind slabs have also been failing at alpine/ treeline elevations, and also running on surface hoar. While the natural activity tapered off since Saturday, the persistent slab is expected to remain reactive to human triggering for several more days.

Snowpack Summary

Wind transported snow has resulted in an added load above the buried persistent weak layer of surface hoar. This has added additional load and stress to an already touchy persistent slab. This 40-90 cm thick persistent slab overlies a variety of surfaces including large surface hoar, sun crusts, rime crusts and facets. The slab is ripe for human and natural triggers and is especially touchy at and below treeline. Rising freezing levels may increase the likelihood of triggering the persistent slab in the short term. The mid and lower snowpack are generally well settled and strong.

Régions couvertes