Bulletin d’avalanche

Northwest Inland

Feb 7 – 8, 2020Avalanche Canada
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Archivé · expiré 7 years ago

Danger d’avalanche

Sun
Mon
Alpin
3 · Marqué
Limite forestière
2 · Modéré
Sous la limite
1 · Faible
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Points saillants

Certain slopes have potential for large persistent slab avalanches. Carefully evaluate the snowpack and terrain before committing to avalanche terrain.

Problèmes avalancheux

  • Wind Slabs

    • Alpin
    • Limite forestière
    • Sous la limite forestière
    Probabilité
    Possible - Likely
    Taille
    1–2

    Recent storm snow is gradually gaining strength, but may remain reactive on steep wind loaded and sun-exposed slopes.

  • Persistent Slabs

    • Alpin
    • Limite forestière
    • Sous la limite forestière
    Probabilité
    Unlikely - Possible
    Taille
    2.5–3.5

    Recent storms have agitated buried weak layers, resulting in some very large persistent slab avalanches. Although these avalanches are only possible in isolated locations, the consequences are severe. Recent areas of concern have been around Kispiox and Hazelton, but any large steep slope should be approached with caution.

Confidence

Moderate - Uncertainty is due to how quickly the snowpack will recover and gain strength.

Weather Forecast

THURSDAY NIGHT: Partly cloudy, light wind from the northwest, alpine temperatures drop to -15 C.

FRIDAY: Mix of sun and cloud, light wind from the east, alpine high temperatures around -10 C.

SATURDAY: Sunny, light wind from the north, alpine high temperatures around -10 C.

SUNDAY: Mix of sun and cloud, moderate wind from the west, alpine high temperatures around -7 C.

Avalanche Summary

Some very large persistent avalanches have been reported over the past week. A size 3 avalanche was triggered by a snowmobiler in the Seaton area on Monday (northeast slope at 1800 m) and a size 3.5 avalanche was remotely triggered by a large snow machine near Kispiox on Saturday (southeast slope at 1700 m). Then on Wednesday, several size 2-3 avalanches were naturally triggered due to strong wind and mild temperatures. These avalanches have ran on both buried surface hoar layers and crust/facets at the bottom of the snowpack.

Some smaller (size 1) wind slabs were also triggered by riders on Wednesday.

Snowpack Summary

Open terrain has been heavily affected by strong wind from the west. Crusts can be found on the surface up to roughly 1200 m and on open south-facing slopes. Some areas continue to have issues with weak layers that formed during cold weather in January. Depending on location these layers may be composed of soft facets or surface hoar and are typically are buried 60-120 cm below the surface. Crust/facet layers also lurk at the base of the snowpack, especially in shallower (eastern) areas. The most recent signs of instability with these deeper layers have been around Hazelton and Kispiox, but persistent weak layers could be a problem on slopes anywhere in the region. 

Terrain and Travel

  • Avoid shallow snowpack areas, rock outcroppings and steep convex terrain where triggering is most likely.
  • Watch for newly formed and reactive wind slabs as you transition into wind affected terrain.

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