Avalanche forecast

Northwest Inland

Feb 28, 2017Avalanche Canada
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Avalanche danger

Tue
Wed
Alpine
3 · Considerable
Treeline
2 · Moderate
Below
1 · Low
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Highlights

Cranking winds accompanied by 5-10 cm will likely build new and reactive wind slabs at upper elevations. Deeper slabs may exist on leeward slopes.

Avalanche problems

  • Wind Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Possible - Likely
    Size
    1–2
    Changing wind directions may form new wind slabs on N-NE aspects. Old wind slabs may continue to linger on southerly aspects due to the recent outflow winds.

  • Deep Persistent Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Unlikely
    Size
    2–4
    A lingering weakness at the bottom of the snowpack may remain sensitive to human triggering, especially in shallow snowpack areas. Surface avalanches in motion also have the potential to step down and trigger deep persistent slabs.

Confidence

Moderate - Intensity of incoming weather systems is uncertain

Weather Forecast

A change in the weather pattern is upon us as the jet shifts to a westerly flow allowing a series of Pacific frontal systems to track across the Interior Coastal Region.Tuesday: Mix of sun and cloud with a trace of new snow 5-8 cm. Alpine temperatures near -9 and ridgetop winds moderate with strong gusts from the SW. Wednesday: Cloudy with scattered flurries. Alpine temperatures near -10 and ridgetop winds moderate with strong gusts from the SW. Thursday: Mostly cloudy with a trace of new snow. Alpine temperatures high of -4 and ridgetop winds moderate-strong from the West. Freezing levels rising to 1000m.

Avalanche Summary

On Sunday, numerous natural wind slabs were reported up to size 1.5 which were triggered by the recent wind event. Previously, there was a report of a size 2.5 natural avalanche in the northern part of the region. This may have happened in the last 5 days and possibly failed on a persistent weak layer buried early february on a NW aspect in the alpine.

Snowpack Summary

Up to 20 cm of storm snow accumulating in the last week has been transported by the wind, and now sits on a variety of old surface conditions including isolated wind slabs, pockets of soft snow (5 to 10 cm deep), sun crusts, and surface hoar. A supportive rain crust exists below 1000 m. A layer of surface hoar that was buried on February 10th may exist 30 to 60 cm below the surface, but there's a fair bit of uncertainty regarding the reactivity and distribution of this layer. A stiff mid pack sits above weak sugary snow near the ground. Although possibly dormant, this basal weakness has the potential to produce very large destructive avalanches.

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