Avalanche forecast

South Columbia

Dec 3 – 4, 2011Avalanche Canada
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Avalanche danger

Mon
Tue
Alpine
3 · Considerable
Treeline
2 · Moderate
Below
1 · Low
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Avalanche problems

  • Wind Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Likely
    Size
    1–4
    Stay vigilant in your terrain and route selection to avoid wind loaded slopes. Switching winds this week have redistributed snow to most aspects. Wind slabs may be found in unsuspecting places.

  • Persistent Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Possible
    Size
    3–6
    Hard to trigger in most areas, but the consequences of triggering a slide on this layer may be a very large avalanche. Weaker thin spots around protruding rocks or clumps of small trees may be likely trigger locations.

Confidence

Fair - Freezing levels are uncertain on Monday

Weather Forecast

A ridge of high pressure is expected to continue to provide drier and cooler temperatures to the interior on Sunday. The temperature should rise on Monday causing the freezing level to rise dramatically to near 3000 metres. Monday evening the ridge is expected to weaken, and light flurries are expected by Tuesday.

Avalanche Summary

Being the start of December more backcountry operations are headed into the field. This means more information, and observations are making there way into our office. Thank you!There is still numerous avalanches occurring in the backcountry. Natural activity up to size 2.0, on various aspects above 2000m have been reported. As well, there are reports of rider triggered activity. On Thursday there was a large (size 3) rider triggered avalanche on a south east aspect at 2900m. The crown depth being 200cm and the slide running 800 vertical meters, over a kilometer. One of the people involved has sustained serious injuries. With the clear, sunny skies ahead don't be fooled. The snowpack is still touchy with weaknesses buried below. Please refer to the Forecaster's Blog for further information and suggestions help you make the right choices in the backcountry. As well, continue to follow our bulletins. We update everyday. Have a safe, fun weekend.

Snowpack Summary

Let's call it 200 cms of snow at the upper boundary of the treeline. There is some variability, so you may find more or less depending on the drainage that you are exploring. If there is 150 cms or less at the treeline-alpine interface elevation, then you are in an area that we would consider having a shallow snowpack. If there is more than 250 cms at this interface, then you are in area with a deep snowpack. Areas with a shallower snowpack are more likely to have a weaker sugary base layer near the ground that may result in large avalanches once this layer has been triggered. Shallow areas may also be more likely to have a weak surface hoar layer about 50 cms above the ground that could be triggered by skiers and riders. Avalanches triggered on this layer could also be quite large, and may propagate across large features. Most reports that we have in this region discuss the widespread wind slab problem in the alpine and at the treeline interface. The wind has come from several different directions, and has been strong enough to re-distribute the snow into hard stiff wind slabs at higher open elevations. The wind slab may be softer as you descend into the trees, but still likely to be triggered.

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