Bulletin d’avalanche

Purcells

Jan 15 – 16, 2013Avalanche Canada
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Archivé · expiré 14 years ago

Danger d’avalanche

Thu
Fri
Alpin
3 · Marqué
Limite forestière
2 · Modéré
Sous la limite
2 · Modéré
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Points saillants

Problèmes avalancheux

  • Wind Slabs

    • Alpin
    • Limite forestière
    • Sous la limite forestière
    Probabilité
    Likely - Very Likely
    Taille
    1–5
    Wind slabs may be found behind terrain breaks such as ridges and ribs. It may be possible for a wind slab to step down to a deeper instability.

  • Persistent Slabs

    • Alpin
    • Limite forestière
    • Sous la limite forestière
    Probabilité
    Possible
    Taille
    1–5
    Persistent weaknesses are variable in their distribution, but can still be triggered by the weight of a person or snowmobile. Triggering persistent slabs will become more likely if the snowpack experiences rapid warming.

Confidence

Fair - Freezing levels are uncertain

Weather Forecast

Wednesday-Friday: Strong north-westerly winds. Freezing level is at valley bottom, with alpine inversions possible (parcels of warm air which could bring alpine temperatures close to 0). Generally only trace amounts of snow.

Avalanche Summary

Several size 1-2 wind slabs were triggered naturally and by skiers on Tuesday morning. Wind slabs were also triggered remotely by a skier and a helicopter on Monday on steep lee slopes.

Snowpack Summary

Strong north-westerly winds have left hard and soft wind slabs in the lee of ridges and ribs at alpine and treeline elevations. Recent storm snow is settling over old snow surfaces including surface hoar (found especially at and below treeline in sheltered areas), a sun crust (on steep S to SW -facing slopes) and facets. The distribution of these weaknesses is patchy, but where they exist, it is still possible to trigger a large avalanche with the weight of a person or snowmobile. Watch out for rapid warming on alpine slopes over the next couple of days, which could weaken the slab above these interfaces. A strong mid-pack overlies a weak facet/crust layer near the base of the snowpack, which is now considered inactive.

Régions couvertes