Bulletin d’avalanche

South Columbia

Apr 15 – 16, 2013Avalanche Canada
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Archivé · expiré 13 years ago

Danger d’avalanche

Wed
Thu
Alpin
3 · Marqué
Limite forestière
2 · Modéré
Sous la limite
1 · Faible
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Points saillants

Problèmes avalancheux

  • Wind Slabs

    • Alpin
    • Limite forestière
    • Sous la limite forestière
    Probabilité
    Possible - Likely
    Taille
    1–4
    Recent snowfall has been redistributed by changing winds. Wind slabs exist on a variety of aspects at treeline and above. Wind has also formed very large and potentially unstable cornices.

  • Persistent Slabs

    • Alpin
    • Limite forestière
    • Sous la limite forestière
    Probabilité
    Possible
    Taille
    1–6
    A weak interface buried down about 60-120 cm has been creating surprisingly large avalanches in neighbouring regions. Incremental loading by snow and wind may have brought the slab above this layer closer to its tipping point.

Confidence

Fair - Due to variable snowpack conditions

Weather Forecast

Tuesday: No snow. Moderate E winds. Freezing level near 1300 m. Wednesday: Light snow. Light SW winds. Freezing level near 1500 m. Thursday: Light snow. Light SW winds. Freezing level near 1600 m.

Avalanche Summary

Several size 1 wind slabs were triggered naturally by wind-loading on Monday. Explosives testing in the south of the region produced slabs up to size 2.5 failing on a crust in cliff terrain. A skier triggered a size 2 cornice and loose snow avalanche on a NE aspect at 2400 m on Sunday.Neighbouring regions: In Glacier National Park, skiers triggered a size 3 slab on a buried crust on an east aspect in the alpine on Monday. On Sunday in the North Columbia region, a helicopter remotely triggered a size 3 slab from 50 m away. It failed on a west aspect at 2450 m, on a crust buried down 60 cm. I suspect these were the same interface. This interface also exists in the South Columbia region.

Snowpack Summary

Up to 40 cm recent storm snow has been shifted by variable winds into reactive wind slabs at treeline and above. A weak interface down about 60-120 cm consists of a crust on solar aspects, and surface hoar on high-elevation northerly aspects. Cornices in the region are very large and potentially destructive. Periods of warming or solar radiation may increase the reactivity of cornices and storm slabs.

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