Avalanche forecast

Northwest Coastal

Dec 8 – 9, 2012Avalanche Canada
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Avalanche danger

Mon
Tue
Alpine
3 · Considerable
Treeline
3 · Considerable
Below
1 · Low
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Highlights

Avalanche problems

  • Wind Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Likely
    Size
    1–4
    New snow combined with forecasted strong northwesterly winds will have created windslabs in the lee of terrain features. Strong winds often create slabs further down the slope than expected and in open areas below treeline.

  • Deep Persistent Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Unlikely
    Size
    2–6
    Deeply buried facet/crust weaknesses are prone to remote triggering and step down avalanches. Typical trigger points include thin rocky areas. They may be difficult to trigger, but deep persistent slab avalanches are often very large and destructive.

Confidence

Poor - Due to limited field observations for the entire period

Weather Forecast

Sunday: Moderate to heavy precipitation throughout the day with strong gusting to extreme northwesterly winds. Alpine temperatures -3 degrees with a freezing level at 1000m. Monday: Heavy precipitation with southwesterly winds 30-50km/h gusting to 90km/h. Freezing levels expected at 800m with alpine temperatures -4 degrees.Tuesday: Light precipitation, temperatures cooling to -7 in the alpine. Winds southwesterly moderate to strong.

Avalanche Summary

Natural activity isolated to the storm snow to size 1.5. Explosives testing north of the Stewart region indicate an avalanche running to size 3.5 in north facing alpine terrain failing in a weak layer of facets near the base of the snowpack.

Snowpack Summary

The storm snow from the past week has settled and been redistributed by the wind from a variety of directions at upper elevations. Alpine and treeline surface snow conditions are variable with buried wind slabs, newly formed wind slabs and areas that are heavily scoured. The mid-pack is gaining strength and is well settled.An November facet/crust layer can be found in the bottom quarter of the snowpack.  We do not have much recent information on this facet/crust interface, so it may be worth digging down yourself to test its reactivity.Total snowpack depth above 1000 m is 150-200 cm deep. Below 1000 m the snowpack shows a sharp transition from 100 cm dropping to 50 cm, and is generally below threshold.

Regions covered