Bulletin d’avalanche

South Columbia

Jan 6 – 7, 2015Avalanche Canada
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Archivé · expiré 12 years ago

Danger d’avalanche

Thu
Fri
Alpin
4 · Fort
Limite forestière
4 · Fort
Sous la limite
3 · Marqué
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Points saillants

High avalanche danger is expected to continue for another day due to new storm slabs, high freezing levels, and above freezing air trapped in the alpine.

Problèmes avalancheux

  • Persistent Slabs

    • Alpin
    • Limite forestière
    • Sous la limite forestière
    Probabilité
    Very Likely
    Taille
    3–6
    The new storm slab may be enough load to trigger the persistent weak layer. Storm slab avalanches in motion may step down to the deeply buried weak layer resulting in large avalanches.

  • Storm Slabs

    • Alpin
    • Limite forestière
    • Sous la limite forestière
    Probabilité
    Very Likely
    Taille
    2–5
    Warm air at the end of the storm has caused rapid settlement in the dry storm slab resulting in increased likelihood of triggering.

Confidence

Poor - Freezing levels are uncertain

Weather Forecast

Snow ending Tuesday night, with a chance of flurries on Wednesday. Warm (above freezing) air that moved into the alpine on Tuesday is forecast to persist on Wednesday. Valley bottoms are forecast to warm up and the freezing level should go up to 1500 metres. The above freezing layer should be between 2000-3000 metres. Moderate to strong Westerly winds are expected on Wednesday afternoon. Gradual clearing and cooling on Thursday with light winds and no precipitation. Mostly clear and cool with light winds on Friday.

Avalanche Summary

Widespread natural and explosives control avalanches up to size 3.0 on Monday. Natural avalanche activity may have ended by Wednesday, but I think that human triggered avalanches will be very likely.

Snowpack Summary

There has been about 60 cm of new snow in the Monashees, and about 50 cm in the Selkirks in the past 48 hours. On Tuesday warm (above freezing) air moved into the alpine and freezing levels climbed up to about 1800 metres. I suspect that the warm temperatures caused rapid settlement in the dry storm slab resulting in a higher likelihood of triggering. Rain or freezing rain have created a moist slab at treeline in the Monashees. The Selkirks may be a bit cooler and drier; alpine temperatures around Revelstoke were -2.0 on Tuesday afternoon.  The new storm slab is 60-80 cm thick and is sitting on a mix of old surfaces including patchy surface hoar and old windslabs on most aspects. Deeper down (around 100 cm) the mid-December surface hoar/crust layer continues to allow for remote triggering and long fracture propagations.

Régions couvertes