Bulletin d’avalanche

Purcells

Mar 13, 2018Avalanche Canada
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Archivé · expiré 9 years ago

Danger d’avalanche

Wed
Thu
Alpin
3 · Marqué
Limite forestière
3 · Marqué
Sous la limite
3 · Marqué
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Points saillants

Avalanche danger will increase on sunny slopes where wet loose avalanches are very likely. Concern is increasing for persistent slabs and cornices.See the Forecaster's Blog for more: http://www.avalanche.ca/blogs/2018-03-09-first-big-warm-up

Problèmes avalancheux

  • Wind Slabs

    • Alpin
    • Limite forestière
    • Sous la limite forestière
    Probabilité
    Possible - Likely
    Taille
    1–2
    Snow and wind from last week have formed variable wind slabs. Slab and loose wet avalanches may be triggered by solar radiation on solar slopes, by cornice fall, or with the weight of a person.

  • Persistent Slabs

    • Alpin
    • Limite forestière
    • Sous la limite forestière
    Probabilité
    Unlikely - Possible
    Taille
    1.5–3
    Rising temperatures and strong sunshine are increasing concern for weak layers buried deep in the snowpack. In addition to human triggering in thin spots, solar warming and cornice releases are possible natural triggers for persistent slabs.

  • Loose Wet

    • Alpin
    • Limite forestière
    • Sous la limite forestière
    Probabilité
    Very Likely - Certain
    Taille
    1–2
    Wet loose avalanches are very likely in steep, rocky, sunny terrain. Warming could also wake up more deeply buried weak layers, creating a surprisingly large avalanche.

Confidence

Moderate - Timing or intensity of solar radiation is uncertain on Tuesday

Weather Forecast

Sunny and warm until light precipitation arrives on Wednesday. TUESDAY: Mainly sunny with some thin cloud. Light southerly winds. Freezing level to 2500 metres with alpine high temperatures of +3.WEDNESDAY: Cloudy with rain or isolated wet flurries (2-5 cm possible). Light to moderate south west winds. Freezing level falling to 1700 metres late in the day, with alpine high temperatures of +1.THURSDAY: Scattered wet flurries (2-5cm). Light southerly winds. Freezing level rising to 2000 metres with alpine high temperatures around 0 degrees.

Avalanche Summary

On Sunday we received reports of a skier caught in a size 2.5 avalanche in the north of the region. The slab was 20-50 cm thick and started on a steep north east aspect immediately below ridge crest at 2300m. See the MIN post for more details. Numerous wet loose avalanches were observed in the region to size 2.5 over the past three days, on sunny aspects. Avalanche activity is expected to increase as we move into a period of intense sun and prolonged warming. Predictable loose wet avalanches from steep, sunny terrain should be easy to manage. The trickier beast will be when warmth penetrates into the snowpack to tickle deeper persistent weak layers. The next few days will be a time to avoid exposure to large sun-exposed features and keep well away from corniced slopes.

Snowpack Summary

Around 10-15 cm of new snow from last week sits on sun crusts on solar aspects. A couple of layers buried in mid-late February (down around 40-100 cm) are variably reactive, but both have the potential to create surprisingly large avalanches if triggered. Initially, these interfaces were most reactive on solar aspects, where they present as buried sun crusts. However, persistent slabs have been triggered on shady aspects too, where surface hoar and/or facets exist (see the Avalanche Summary above for more information).Deeper persistent weak layers from January and December are generally considered dormant, but could wake up with forecast warming, a surface avalanche stepping down, cornice fall, or a human trigger in a shallow or variable-depth snowpack area. These layers consist of sun crust, surface hoar and/or facets. Facets also linger at the base of the snowpack.

Régions couvertes