Bulletin d’avalanche

Northwest Inland

Feb 5 – 6, 2015Avalanche Canada
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Archivé · expiré 12 years ago

Danger d’avalanche

Sat
Sun
Alpin
4 · Fort
Limite forestière
4 · Fort
Sous la limite
3 · Marqué
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Points saillants

Extreme winds coupled with new snowfall is expected to drive a natural avalanche cycle Friday. Probably best to stay out of avalanche terrain while the storm is raging.

Problèmes avalancheux

  • Persistent Slabs

    • Alpin
    • Limite forestière
    • Sous la limite forestière
    Probabilité
    Possible
    Taille
    2–5
    The late-Jan crust is down 60-80cm and may still be reactive in some areas. In the mid-pack there are older persistent weak layers but these have generally stabilized. Extra caution is required in thinner snowpack areas, especially the north.

  • Storm Slabs

    • Alpin
    • Limite forestière
    • Sous la limite forestière
    Probabilité
    Likely
    Taille
    1–4
    New snow will add to the existing 20-30 cm of recent storm snow which is likely settling into a slab.  Strong to extreme SW winds should form large wind slabs in everything but the most sheltered terrain.

  • Deep Persistent Slabs

    • Alpin
    • Limite forestière
    • Sous la limite forestière
    Probabilité
    Unlikely
    Taille
    3–6
    Although less likely to trigger, recent avalanche activity suggests weak layers buried at the beginning of the winter should still be our radar, especially in the north of the region.

Confidence

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

Weather Forecast

Extreme southerly winds in the alpine along with strong east through south winds below treeline are expected through the forecast period. The freezing level should stay right at valley bottom and a few shots of precipitation are expected. 5 to 10 cm are possible Thursday night, another 5 to 10cm are expected Friday with 5 to 10cm on tap for Friday night. For a more detailed look at this dynamic weather pattern visit avalanche.ca/weather

Avalanche Summary

A number of size 1 to 2 avalanches in the recent storm snow were reported Wednesday.  Small wind slabs near ridge crest were reported Tuesday to size 1. On Monday, natural and human-triggered avalanches size 1 to 1.5 were reported in the south of the region. These were 20-30cm thick in sheltered areas and 30cm+ in wind loaded features. Sluffing from steep terrain was also reported.

Snowpack Summary

20 - 30cm of new snow has fallen in the last couple days. Strong winds have redistributed this snow in exposed terrain forming winds slabs in leeward features and stripping exposed slopes. The late-January crust is typically down 60-80cm in the south of the region and probably around half this depth in the north. Tests are indicating that this interface is generally well bonded, but isolated avalanches have been reported to have released on this layer recently. The mid-January rain crust and/or surface hoar layer is down over 1m in the south and has generally become inactive. It may still be a concern in thinner snowpack areas, at higher elevations, and in the far north of the region. Near the base of the snowpack is a crust-facet combination buried in November. This deep persistent weakness was recently reactive and may still be touchy in the far north of the region. Wherever you are, I'd be cautious of this deep and potentially destructive layer. Possible triggers include thin spot triggering in high elevation terrain, a cornice fall, or a smaller avalanche stepping down.

Régions couvertes