Bulletin d’avalanche

Kootenay Boundary

Mar 19 – 20, 2020Avalanche Canada
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Archivé · expiré 7 years ago

Danger d’avalanche

Sat
Sun
Alpin
1 · Faible
Limite forestière
2 · Modéré
Sous la limite
1 · Faible
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Points saillants

Avalanche danger is on a declining trend, however remain careful on steep slopes at treeline elevations.

Problèmes avalancheux

  • Persistent Slabs

    • Alpin
    • Limite forestière
    • Sous la limite forestière
    Probabilité
    Unlikely
    Taille
    1.5–2.5

    A weak layer of surface hoar exists 40 to 80 cm below the surface and has produced a few large avalanches over the past weeks. This problem seems most prevalent on northwest to northeast aspects between 1700 m and 2100 m. 

    While the likelihood of triggering a persistent slab avalanche is dropping, there is still some uncertainty about where and for how long this problem will persist.

Confidence

High - We have a good understanding of the snowpack structure and confidence in the weather forecast

Weather Forecast

A high pressure system brings clear dry conditions until Monday (at least).

THURSDAY NIGHT: A few clouds, light northwest wind, freezing level drops to valley bottom, alpine temperatures drop to -6 C.

FRIDAY: Sunny, light to moderate northwest wind, freezing level climbing to 1800 m in the afternoon, alpine temperatures reach -1 C. 

SATURDAY: Mix of sun and cloud, light northwest wind, freezing level climbing to 1800 m in the afternoon, alpine temperatures reach -1 C.

SUNDAY: Mostly sunny, light northwest wind, freezing level climbing to 1500 m in the afternoon, alpine temperatures reach -4 C.

Avalanche Summary

Recent avalanche activity has primarily been small (size 1-1.5) wet loose avalanches in steep south-facing terrain. Persistent slab avalanche activity has quieted down over the past two weeks, with only a few small to large (size 1-2) avalanches releasing on the late February surface hoar layer. They have most often released between 1700 m and 2100 m on northwest to east aspects.

Looking forward, daytime warming may create potential for small loose wet avalanches on steep sun-exposed slopes. If you decide to travel in the backcountry, consider sharing your observations with us and fellow recreationists via the Mountain Information Network (MIN) to supplement our data stream as operators are shutting down. Even just a photo of what the day looked like would be helpful.

Snowpack Summary

Surface conditions are highly variable with a mix of crusts, moist snow, and hard wind slabs. The surface will become moist on sun-exposed slopes and at lower elevations throughout the day. A few different layers of surface hoar and melt-freeze crust exist in the upper snowpack. These layers have produced some isolated avalanches over the past two weeks and remain possible to trigger. One layer was buried a week ago and may be found about 10 to 30 cm deep, but the most widespread layer was buried in late February and is now 40 to 80 cm deep. This layer is most commonly found in open trees (e.g. in this MIN). The remainder of the snowpack is strong and well-settled.

Terrain and Travel

  • Carefully assess open slopes and convex rolls where buried surface hoar may be preserved.
  • Carefully evaluate steep lines for wind slabs.
  • The more the snowpack warms-up and weakens, the more conservative you`ll want to be with your terrain selection.

Régions couvertes