Bulletin d’avalanche

Purcells

Apr 3 – 4, 2013Avalanche Canada
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Archivé · expiré 13 years ago

Danger d’avalanche

Fri
Sat
Alpin
2 · Modéré
Limite forestière
2 · Modéré
Sous la limite
2 · Modéré
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Points saillants

Be alert to conditions that change with daytime warming. Danger ratings are likely to exceed posted levels if solar radiation is strong, especially at treeline and below.

Problèmes avalancheux

  • Cornices

    • Alpin
    • Limite forestière
    • Sous la limite forestière
    Probabilité
    Possible
    Taille
    1–5
    Natural cornice falls are a concern during daytime warming. Cornices may also be triggered easily by traveling near them.

  • Persistent Slabs

    • Alpin
    • Limite forestière
    • Sous la limite forestière
    Probabilité
    Unlikely - Possible
    Taille
    2–6
    Small solar triggered slides, cornice fall, or thin-spot triggering may overload a persistent weakness buried 100 cm deep. This could lead to surprisingly large avalanches.

  • Loose Wet

    • Alpin
    • Limite forestière
    • Sous la limite forestière
    Probabilité
    Possible - Likely
    Taille
    1–4
    Expect to see wet loose snow avalanches out of steep rocky sun-exposed slopes if the sun comes out. Natural avalanche activity. snowballing, moist and wet snow surfaces are all initial indications of the upper snowpack deteriorating.

Confidence

Fair - Freezing levels are uncertain for the entire period

Weather Forecast

Thursday: A weak high pressure system builds promoting clear and dry conditions with light westerly winds and 2000m freezing levels.Friday: An upper trough of low pressure will move over the Interior late Thursday through Friday bringing moderate to locally heavy precipitation. Freezing levels will be around 1900m. Winds light to moderate from the west.Saturday: Overcast with light precipitation possible. Winds light from the south.

Avalanche Summary

Numerous natural loose wet avalanches up to size 2.5 and one natural cornice fall size 2.5.

Snowpack Summary

Surface faceting and surface hoar growth (up to 20 mm) has been prevalent on high, shady aspects, while the surface snow on sun-exposed slopes and at lower elevations (below 2000m) has been subject to daily melt-freeze cycles. Cornices are large and weak. A layer of buried surface hoar sitting on a crust down around 70-120cm, and has been producing variable results in snowpack tests. This persistent weakness remains a concern because of the potential for very large avalanches particularly with heavy triggers such as cornice falls. Old deep persistent weaknesses, including basal depth hoar, are a concern in shallow snowpack areas.

Régions couvertes