Avalanche forecast

Northwest Coastal

Dec 28 – 29, 2015Avalanche Canada
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Avalanche danger

Wed
Thu
Alpine
3 · Considerable
Treeline
3 · Considerable
Below
2 · Moderate
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Highlights

Touchy avalanche conditions are expected to persist. If you have questions about the snowpack, conservative terrain selection is always the answer.

Avalanche problems

  • Persistent Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Unlikely - Possible
    Size
    2–4
    A few buried surface hoar layers exist in the top 100cm of the snowpack. I would keep these on my radar on steep unsupported slopes, especially at treeline and below.

  • Storm Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Possible - Likely
    Size
    1–3
    Up to 40cm of recent storm snow overlies a weak mix of facets and surface hoar. I'd be extra cautious in wind-affected areas where the new snow exists as a cohesive slab. Touchy conditions should persist for the forecast period.

Confidence

Moderate - Wind effect is extremely variable

Weather Forecast

A ridge of high pressure has set up over the province and will bring mainly clear skies for the forecast period. Ridgetop winds should remain light and northwesterly on Tuesday and Wednesday. Winds will switch to southwesterly on Thursday intensifying throughout the day. Alpine temperatures should sit at about -10 on Tuesday and Wednesday with an inversion developing on Thursday.

Avalanche Summary

Evidence of natural storm slab avalanches to size 2 was observed in the wake of Saturday's storm. In sheltered terrain, loose dry avalanche activity has also been noted. Natural avalanche activity will likely taper-off with the current clearing trend. However, human-triggered avalanches will remain a concern for the forecast period, especially at elevations or in parts of the region where recent storm accumulations have settled into a cohesive slab.

Snowpack Summary

Last weekend, between 25cm and 40cm of new snow fell. Winds associated with the storm were highly variable. In areas (or at elevations) where the wind was strong, there may be a cohesive and reactive storm slab. In areas where the winds were light, you're more likely to find loose powder. The new snow overlies a touchy layer of sugary faceted snow and well-developed surface hoar which is reported to exist on all aspects and elevations. Due to the persistent nature of these underlying crystals, newly formed storm slabs may remain reactive for the foreseeable future. Adding to the mix of weaknesses in the upper snowpack are a few other surface hoar layers that developed throughout December which you may now find buried in the top 100cm. The weight of the new snow (or a surface avalanche in motion) may cause these layers to "wake up" resulting in larger, more destructive avalanches.

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