Avalanche forecast

Kootenay Boundary

Feb 20 – 21, 2012Avalanche Canada
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Avalanche danger

Wed
Thu
Alpine
4 · High
Treeline
4 · High
Below
3 · Considerable
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Highlights

Many parts of the region will reach the tipping point with forecast new snow and wind for Tuesday. Large, easily triggered avalanches are very likely.

Avalanche problems

  • Wind Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Likely
    Size
    2–6
    Forecast strong to extreme winds will set up new wind slabs behind exposed terrain features in the alpine and at treeline.

  • Persistent Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Likely
    Size
    2–6
    A persistent weak layer comprising surface hoar in sheltered areas, a crust on solar aspects and facets elsewhere lies buried 30-40 cm below the surface. With additional snow load, avalanches with potential for size 3 are possible.

  • Deep Persistent Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Unlikely - Possible
    Size
    3–7
    Large avalanches remain a concern in shallow rocky areas where they could be triggered with a very heavy load, such as cornice fall.

Confidence

Poor - Intensity of incoming weather is uncertain

Weather Forecast

Tuesday: A Pacific frontal system arrives bringing 10-15 cm new snow and strong westerly winds, which at ridge top could reach 100 km/h. Freezing levels will spike to around 1500 m in the afternoon. Wednesday: the cold front associated with the system moves through, bringing further moderate amounts of snow and bringing freezing levels down to around 1000 m. Winds should become moderate northwesterly. Thursday: Dry, with light northwesterly winds and freezing levels around 800 m.

Avalanche Summary

Numerous size 1 and 2 avalanches have been reported from this region, running on a variety of aspects and elevations and with crowns up to 40 cm deep.

Snowpack Summary

Snowfall Sunday night added a further 10-20 cm, bringing the amount of snow that now lies above the early February weak layer to around 40 cm. This is right at the critical depth where triggering is very likely and resulting avalanches could easily be large enough to bury a person. The early February weak layer comprises large surface hoar on sheltered aspects, facets on northerly aspects and a crust on solar aspects--professionals are treating this layer with extreme caution, since it is showing signs of remote triggering and the ability to propagate in low angled terrain. Alpine winds have been strong enough to blow snow around, adding touchy wind to the problem, especially behind exposed terrain features in the alpine. In shallow snowpack areas concerns remain for the mid-December persistent weakness down around 80-100cm and for basal facets. Treeline snowpack depths are approximately 230 cm.

Regions covered