Bulletin d’avalanche

Northwest Inland

Jan 27 – 28, 2015Avalanche Canada
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Archivé · expiré 12 years ago

Danger d’avalanche

Thu
Fri
Alpin
3 · Marqué
Limite forestière
3 · Marqué
Sous la limite
1 · Faible
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Points saillants

The storm may have tapered-off, but persistent weaknesses have to the potential to surprise with nasty consequences. Conservative terrain selection remains critical.

Problèmes avalancheux

  • Persistent Slabs

    • Alpin
    • Limite forestière
    • Sous la limite forestière
    Probabilité
    Possible - Likely
    Taille
    1–4
    Recent avalanche activity indicates a crust/surface hoar combo, which formed in January, should remain on our radar. Due to the persistent nature of these crystals, I would expect ongoing reactivity with the potential for large avalanches.

  • Storm Slabs

    • Alpin
    • Limite forestière
    • Sous la limite forestière
    Probabilité
    Possible - Likely
    Taille
    1–3
    A storm on Monday night has built new storm slabs. In recent days, avalanches have failed within the storm snow, and "stepped-down" to deeper layers resulting in surprisingly large avalanches. Use increased caution in wind-affected terrain.

  • Deep Persistent Slabs

    • Alpin
    • Limite forestière
    • Sous la limite forestière
    Probabilité
    Possible
    Taille
    2–6
    In recent days, heavy loading from wind, snow and/or rain has triggered deep persistent weaknesses. Large destructive avalanches remain a concern, and may reach the end of their run-outs.

Confidence

Fair - Due to the number of field observations

Weather Forecast

Generally light snowfall, strong southwest winds and freezing levels at 600m are expected on Wednesday. Snowfall is expected to intensify Wednesday evening and continue throughout Thursday. By Friday morning, we can expect up to 15cm of accumulated snowfall. Winds are forecast to remain strong and southwesterly during the system, and then become light and northwesterly as the snowfall tapers-off on Friday. Freezing levels should hover around 800m for Thursday and Friday.

Avalanche Summary

A few close calls on Sunday suggest that the region has undergone a fairly active avalanche pattern. In the Hankin area, a skier accidentally triggered a size 2.5 avalanche which resulted in a full burial and minor injuries. The avalanche was reported to have occurred on a wind-loaded, north-facing slope. The avalanche initially failed on the January crust/surface hoar combo, and then stepped-down to the November crust and basal facets. Thanks to the party involved for sharing this information, and good work on a quick and effective companion rescue.On the same day in the Sinclair area, a snowmobile may have been the trigger for a size 3 avalanche. The avalanche had a crown between 1 and 2 metres, and propagated up to 200 metres wide.  It occurred on a wind-loaded, north-facing alpine slope and may have failed on the November crust facet combo. Given the persistent nature of these weak layers, there is ongoing potential to trigger these deeper, destructive layers.

Snowpack Summary

Moderate to heavy snowfall (with rain at lower elevations) and strong southwest winds have built deep and dense storm slabs. These storm slabs are expected to be most reactive in wind-exposed, upper elevation terrain. A rain crust and/or surface hoar layer buried mid-January may be found between 60- 100cm below the surface. This persistent weakness has been reactive with recent storm loading. Near the base of the snowpack is the crust-facet combination buried in November. This deep persistent weakness seems to have "woken-up" in some terrain in response to warming and heavy loading from wind and snow.

Régions couvertes