Avalanche forecast

South Rockies

Jan 8 – 9, 2012Avalanche Canada
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Avalanche danger

Tue
Wed
Alpine
3 · Considerable
Treeline
3 · Considerable
Below
1 · Low
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Avalanche problems

  • Wind Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Likely
    Size
    1–4
    Wind slabs will have formed on lee and cross-loaded aspects at treeline and in the alpine. As well, expect weak cornices at ridge crests as they can be a trigger for the slope below.

  • Persistent Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Possible - Likely
    Size
    3–6
    A cohesive slab sits over a touchy surface hoar/ facet weakness buried in mid-December. Slides are still occurring on this layer. Avalanches on this layer will be large, destructive and more difficult to predict.

Confidence

Fair - Intensity of incoming weather is uncertain on Monday

Weather Forecast

Monday: 8-10cm of snow (less on the east side of the region) / moderate to strong southwest winds / Freezing level at 1200m (1900m on the east side of the region)Tuesday: A mix of sun and cloud with light snowfall / light to moderate northwest winds / Freezing level at surfaceWednesday: Clear skies / Light to moderate northerly winds / Freezing level at surface

Avalanche Summary

A sled-triggered size 3 slab avalanche was reported from the Flathead/ Lodgepole area on saturday. The slide was 75cm deep and 100m wide and occurred on a northeast aspect at the 2100m elevation. Size 1.5 loose snow avalanches were reported in the Elkford area on Saturday.Please visit our incident report database (under bulletins) on our website for more details.

Snowpack Summary

The average HS (height of snow) in the Crowsnest North is 120cms and the Crowsnest South has 150cms. As we move further West into the Elk Valley North the HS is an average of 130cms. The Elk Valley South sits at 170cms.In the Flathead the avg. HS is 170cms. All snow depths indicated are at the 2000m elevation.In the alpine and exposed slopes at treeline windward aspects have been stripped of snow by strong winds over the past week, and lee slopes have widespread stiff wind slabs. Over the past few days, dribs and drabs of new snow has added to an overriding unconsolidated soft slab.In the mid pack, weak buried surface hoar layers can be found on North-NE slopes at treeline and below down approx. 30-55cms. The surface hoar may co-exist with facets that are result of the early December dry spell. This interface is still reactive and has produced numerous natural avalanches over the past week.At the bottom of the snowpack a variable facet/ crust/ facet sandwich is located with depth hoar up to size 5mm below the crust, and facets size 2mm above. There has been little in the way of recent activity on basal layers, but the nature of a release would be highly destructive.As a side note, the snow depths alone indicate that the region is highly variable in terms of snowpack structure. You should anticipate that layering and reactivity of weaknesses will also be variable throughout the region.

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