Bulletin d’avalanche

Northwest Coastal

Jan 7 – 8, 2013Avalanche Canada
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Archivé · expiré 14 years ago

Danger d’avalanche

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

Danger appears to be heightened in the backcountry near Terrace.

Problèmes avalancheux

  • Storm Slabs

    • Alpin
    • Limite forestière
    • Sous la limite forestière
    Probabilité
    Possible
    Taille
    2–5
    Storm snow is bonding poorly with buried surface hoar buried around 60cm, creating a touchy storm slab problem. Wind slabs have formed predominantly on westerly and northerly aspects.

Avalanche Summary

A cycle of natural and human-triggered (including remotely-triggered and helicopter-remote) avalanches of up to size 2.5 was observed on Thursday and Friday across the region. The storm snow was propagating easily on buried surface hoar and facets. Since then, the new snow appears to have produced fewer natural avalanches, but the potential for further avalanche activity during storms or due to human triggering is still there.

Confidence

Poor - Due to limited field observations

Weather Forecast

Tuesday: There may be some lingering light snowfall but the frontal system affecting the south coast is too far south to impact this region. Winds gusting to 40 km/h from the west. Freezing level around 200m. Wednesday and Thursday: Dry and getting progressively colder as arctic air moves in. Winds switching to northerly. Ridgetop winds should be mostly light, although stronger outflow winds at lower elevations are a possibility.

Snowpack Summary

40-90cm of recent storm snow is bonding poorly to old snow surfaces, especially near Terrace. The old snow surfaces comprise of surface hoar crystals and/or facets. A few days ago, this layer was being triggered naturally or remotely and propagating widely. Near Bear Pass, reports indicate the storm snow may be bonding slightly better. Recent strong southwesterly to easterly winds have set up wind slabs in many exposed lee areas. There are two surface hoar layers in the upper snowpack. The upper one formed at the end of December and is buried on average 50 cm below the surface. This one is particularly reactive at present. The lower one formed at the beginning of December and is buried more than a metre below the surface. There are no recent reports of activity on this layer. Near the base of the snowpack, a crust/facet layer continues to give hard, sudden results to no results in snowpack tests. This weakness is unlikely to be triggered by a single person, but it remains possible with a very heavy load (e.g. cornice fall) or from a thin-spot trigger point.

Régions couvertes