Lawinenlagebericht

Kootenay Boundary

Feb 5 – 6, 2021Avalanche Canada
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Lawinengefahr

Sun
Mon
Hochgebirge
3 · Erheblich
Waldgrenze
3 · Erheblich
Unterhalb
3 · Erheblich
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Kernpunkte

A weak layer of surface hoar has produced very large avalanches in recent days at treeline and below. Stick to low angle terrain and exercise a high degree of caution around open glades and leeward terrain features.

Lawinenprobleme

  • Wind Slabs

    • Hochgebirge
    • Waldgrenze
    • Unterhalb der Waldgrenze
    Wahrscheinlichkeit
    Likely - Very Likely
    Größe
    1–2

    Wind slabs may continue to be reactive and easily triggerable by humans at upper elevations.

  • Persistent Slabs

    • Hochgebirge
    • Waldgrenze
    • Unterhalb der Waldgrenze
    Wahrscheinlichkeit
    Possible
    Größe
    2–3

    50-80 cm of snow sits on a persistent weak layer that was buried near the end of January. This layer consists of a melt-freeze crust in some areas, surface hoar in sheltered areas, and facets in some areas. This layer has been the most reactive at treeline and below treeline, where it exists as surface hoar.

    Another layer of surface hoar that was buried in mid-January may still be possible to trigger, and it is now down about 80-100 cm.

Confidence

High - The number, quality, or consistency of field observations is good, and supports our confidence.

Weather Forecast

Thursday night: Flurries, up to 5 cm new snow, moderate to strong westerly wind, alpine temperature near -10.

Friday: Mix of sun and cloud, moderate to strong northwest wind, alpine high -5, freezing level 1500 m.

Saturday: Mainly cloudy, moderate southwest wind, alpine high -7, freezing level valley bottom.

Sunday: Mix of sun and cloud, moderate northwest wind, alpine high -12, freezing level valley bottom.

Avalanche Summary

There have been numerous natural, human and explosives triggered avalanches reported over the last couple of days, up to size 3.5. Most of these avalanches failed on the recently buried persistent weak layer. Many occurred at elevations around treeline where the layer exists as surface hoar.

It is notable that a size 3.5 was reported to have failed on a crust that was buried in early December. A smaller avalanche stepped down to this deeper layer, resulting in a very large and destructive avalanche.

Snowpack Summary

20-40 cm of snow sits on a freezing rain crust in some parts of the region. It is not known how widespread this layer is, but it may have the potential to produce avalanches where it exists.

There is now about 50-80 cm of recent storm snow sitting above a persistent weak layer that consists of facets in some areas, a melt-freeze crust in many areas, on a sun crust on steep south-facing slopes, and large surface hoar in sheltered areas. This layer has been the most reactive at treeline and below treeline, where it exists as surface hoar.

There are potentially several more layers of surface hoar in the upper snowpack, with the most notable one down about 80-120 cm. This layer was buried in early January. 

A crust surrounded by weak faceted grains is buried deep within the snowpack. It may be possible to trigger this layers with a large load.

Terrain and Travel

  • Be aware of the potential for large avalanches due to the presence of buried surface hoar.
  • Keep in mind that human triggering potential persists as natural avalanching tapers off.
  • Avoid freshly wind loaded terrain features.

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