Bulletin d’avalanche

Northwest Coastal

Feb 4 – 5, 2015Avalanche Canada
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Archivé · expiré 12 years ago

Danger d’avalanche

Fri
Sat
Alpin
3 · Marqué
Limite forestière
3 · Marqué
Sous la limite
3 · Marqué
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Points saillants

Thursdays danger ratings are based on the storm arriving fairly late in the day. If it arrives earlier, the danger could quickly rise to high.

Problèmes avalancheux

  • Persistent Slabs

    • Alpin
    • Limite forestière
    • Sous la limite forestière
    Probabilité
    Possible
    Taille
    3–6
    This storm system should be a good test for the more deeply buried weak layers.  With up to a meter of new snow expected in the alpine by Saturday afternoon, I wouldn't be surprised to see storm slabs step down to one of the persistent weaknesses.

  • Storm Slabs

    • Alpin
    • Limite forestière
    • Sous la limite forestière
    Probabilité
    Likely - Very Likely
    Taille
    1–3
    Significant storm snow and strong wind will likely initiate a large natural avalanche cycle by Thursday night.  I expect the cycle to continue through the day Saturday.

Confidence

Fair - Timing of incoming weather systems is uncertain on Thursday

Weather Forecast

The first of three distinct waves of well organized precipitation accompanied by strong S/SW winds should impact the North Coast Thursday afternoon. The second wave should arrive mid-day Friday with the final wave colliding into the region Saturday. Cold Arctic air mixing should keep the freezing level right around 500m throughout the storm. With 25 to 95 mm of water expected from the storm, total alpine snow totals in excess of one meter aren't out of the question.

Avalanche Summary

On Monday and Tuesday wind and storm slab avalanches to size 1.5 ran both naturally and with human provocation. Sluffing from steep terrain was also reported.

Snowpack Summary

30- 50cm of new snow has fallen in the last few days. Strong winds have redistributed this snow in exposed terrain forming winds slabs in leeward features and stripping exposed slopes. The late-January crust is typically down 100-140cm in the south of the region and about half this depth in the north. Tests are indicating that this interface is generally well bonded but isolated avalanches have been reported to have released on this layer recently. The mid-January rain crust and/or surface hoar layer is down over 150cm in the south and has generally become inactive. It may still be a concern in thinner snowpack areas. The November crust/facet combo near the bottom of the snowpack is thought to be generally well bonded. However, this deep and destructive layer is still reported to be reactive in the far north of the region.

Régions couvertes