Bulletin d’avalanche

Purcells

Dec 13 – 14, 2013Avalanche Canada
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Archivé · expiré 13 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

New snow, wind, and warm temperatures will drive the avalanche hazard over the weekend.

Problèmes avalancheux

  • Wind Slabs

    • Alpin
    • Limite forestière
    • Sous la limite forestière
    Probabilité
    Likely
    Taille
    1–3
    Deep and touchy winds slabs are lurking below ridge crests and behind terrain features on lee and cross-loaded slopes. Expect wind slab development to continue for the forecast period.

  • Persistent Slabs

    • Alpin
    • Limite forestière
    • Sous la limite forestière
    Probabilité
    Unlikely - Possible
    Taille
    2–5
    Persistent weakness may become more touchy with forecast warming and additional load from new snow and wind. This includes mid-pack surface hoar (more of a concern in deeper snowpack areas), and basal facets (more of a concern in shallow areas).

Confidence

Fair - Due to the number of field observations

Weather Forecast

Saturday: Cloudy with flurries expected to bring no more around 5cm of new snow. Freezing levels expected to remain at or near valley bottoms with treeline temperatures around -2. Ridge top winds are expected to be moderate westerlies. Sunday: Moderate snowfall with 10-15cm of accumulation, freezing levels rising up to 1800m and strong southwesterly winds. Monday: Light snowfall with less than 5cm of accumulation, freezing levels around 1500m and strong westerly winds.

Avalanche Summary

Reports from yesterday are limited to a few loose sluffs from steep terrain. On Tuesday, a wind slab avalanche size 1.5 was easily triggered under the weight of a rider from a NE aspects.

Snowpack Summary

Light incremental snowfall is starting to bury surface hoar and a faceted upper snowpack. Snowpack depths at treeline seem to vary from 70 - 110 cm with high variability in wind-exposed areas. A persistent weakness of buried surface hoar and facets, with an associated crust, is down approximately 20-40cm . Recent reports suggest this layer has been producing variable results with snowpack tests, but it may become reactive as a cohesive slab develops with warming and/or additional load. The base of the snowpack is made up of weak facets and depth hoar. This deep persistent weakness may be stubborn to trigger, especially in deeper snowpack areas, but the sensitivity to triggers likely increases in shallower locations, especially on a steep, convex slopes.

Régions couvertes