Avalanche forecast

Northwest Coastal

Dec 27 – 28, 2013Avalanche Canada
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Avalanche danger

Sun
Mon
Alpine
3 · Considerable
Treeline
3 · Considerable
Below
2 · Moderate
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Highlights

Avalanche problems

  • Persistent Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Possible
    Size
    3–7
    Mainly an issue in the northern part of the region where the snowpack is less deep and a weakness of facets and/or a crust is found near the base of the snowpack. 

  • Storm Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Likely
    Size
    1–4
    It will be possible to trigger deep storm and wind slabs in steeper terrain, especially on exposed N-E aspects and at higher elevations where a surface rain crust does not form.

Confidence

Fair - Forecast snowfall amounts are uncertain

Weather Forecast

Saturday: Cloudy with flurries or periods of snow developing later in the day 5-15 cm. The freezing level is near 500 m and winds are light from the NW switching to moderate W-SW. Sunday: Periods of snow, easing in the afternoon 10-20 cm. The freezing level should climb to around 1500 m and winds are moderate to strong from the W-SW. Monday: Periods of snow. The freezing level lowers to around 1000 m.

Avalanche Summary

Observations during the storm yesterday are very limited; however, there was one report of loud rumbling in the Shames backcountry. I would expect a fairly widespread and large natural avalanche cycle occurred. Natural avalanche activity should taper off heading into the weekend, but rider triggering remains a concern. Lower elevation explosive control on Thursday also produced wet avalanches up to Size 2.5.

Snowpack Summary

Southern Sections: The Boxing Day blitz dumped another 50-80 cm of heavy snow, accompanied by strong southwest winds. Freezing levels peaked near 2000 m right along the coast and around 1400 m further inland towards Terrace. Recently buried weaknesses of surface hoar and/or facets are now well over 1 m deep and were likely flushed out or squashed by the heavy snowfall. Forecast cooling should help stabilize the snowpack and result in a surface crust forming below treeline. Northern Sections: Storm snow totals are closer to 30-40 cm. Fresh dense wind slabs are likely in exposed lee terrain and cross-loaded features. A recently buried surface hoar layer is now down around 50-60 cm and is likely primed for rider triggering. A facet/crust layer exists near the base of the snowpack, primarily on higher NW through E facing slopes. Triggering this layer may be unlikely, but if triggered the resulting avalanche would be very large and dangerous.

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