Lawinenlagebericht

Kootenay Boundary

Dec 28 – 29, 2020Avalanche Canada
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Lawinengefahr

Wed
Thu
Hochgebirge
3 · Erheblich
Waldgrenze
2 · Mässig
Unterhalb
2 · Mässig
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Kernpunkte

Watch out for lingering wind slabs which may remain sensitive to human triggers. Be mindful that buried weak layers are still present and are best managed through conservative terrain selection.

Lawinenprobleme

  • Wind Slabs

    • Hochgebirge
    • Waldgrenze
    • Unterhalb der Waldgrenze
    Wahrscheinlichkeit
    Possible
    Größe
    1–2

    Lingering wind slabs remain reactive to human traffic in lee features such as below ridge crests and roll-overs.

  • Persistent Slabs

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

    Weak layers of surface hoar and/or faceted grains overly a hard melt-freeze crust around 60 to 80 cm deep. New snow loads before Christmas pushed the persistent slab problem over the tipping point resulting in large avalanches. Although the likelihood of triggering a persistent slab avalanche is decreasing, the potential for triggering a high consequence avalanche should still be top of mind in your decision making process. 

Confidence

Moderate - Uncertainty is due to the limited number of field observations.

Weather Forecast

Sunday night: Partly cloudy, light southwest wind, freezing level valley bottom.

Monday: Sunny, light northwest wind, alpine temperature -7 C, freezing level valley bottom.

Tuesday: Increasing cloud, light northwest wind, alpine temperature -7 C, freezing level valley bottom.

Wednesday: Cloudy, light to moderate southwest wind, alpine temperature -6 C, freezing level valley bottom.

Avalanche Summary

A couple of skier triggered size 1 avalanches were reported over the weekend, a wind loaded pocket below a roll-over (here) and isolated loose dry sluffs in the new snow.

Many storm and persistent slab avalanches were observed last week across the region. They were generally large (size 2), on west, north, and east aspects, 20 to 70 cm thick, and between 2000 and 2300 m. Although avalanche activity is becoming smaller and more sporadic, the potential to trigger buried weak layers remains.

Snowpack Summary

5-15 cm of recent snow sits over surface hoar in wind sheltered areas. Lingering wind slabs formed last week may remain reactive on a variety of aspects due to shifting winds.

Two weak layers are buried in close proximity to one another, around 50 to 80 cm deep. The layers are composed of feathery surface hoar and sugary faceted grains and they overly a hard melt-freeze crust. Last week saw substantial avalanche activity on these layers from natural and human triggers. Although reports of such avalanches have been dwindling, these weak layers remain a concern, as they can produce large and destructive avalanches.

Terrain and Travel

  • Be careful with wind loaded pockets, especially near ridge crests and roll-overs.
  • If triggered, wind slabs avalanches may step down to deeper layers resulting in larger avalanches.
  • Uncertainty is best managed through conservative terrain choices at this time.

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