Avalanche forecast

South Rockies

Dec 13 – 14, 2015Avalanche Canada
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Avalanche danger

Tue
Wed
Alpine
3 · Considerable
Treeline
2 · Moderate
Below
1 · Low
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Highlights

The weekend's storm instabilities are expected to linger for a few days.Use extra caution on steep south-facing slopes during the afternoon if the sun is out in full force.

Avalanche problems

  • Wind Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Possible
    Size
    1–2
    Recent wind slabs are expected to remain reactive to human-triggering, especially in the leeward side of ridge crests and in wind-loaded chutes.  The sun may increase the likelihood of triggering storm instabilities on steep, south-facing slopes.

  • Persistent Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Unlikely - Possible
    Size
    2–5
    A weakness buried early-Dec and a rain crust from mid-Nov in the mid-pack are becoming difficult to trigger but are still a concern in isolated areas.  Heavy triggers like cornices or avalanches stepping down could result in very large avalanches.

Confidence

Moderate - Timing or intensity of solar radiation is uncertain

Weather Forecast

A ridge of high pressure will bring dry and mostly sunny conditions on Monday. Freezing levels are expected to be around 1000m in the afternoon and ridgetop winds should be light from the north. A mix of sun and cloud is expected for Tuesday with freezing levels falling to valley bottom and light alpine winds from the NW. Light snowfall is being forecast for Wednesday.

Avalanche Summary

On Friday, ski cutting produced size 1 soft slabs in immediate lee features (generally north through east aspects). On Saturday, explosives and ski cutting produced storm slabs size 1-2 which were typically 20-60cm thick. On Sunday, explosives triggered a few size 2 wind slabs which were typically 30cm thick.

Snowpack Summary

The series of storms last week produced 70-90cm of new snow in the region. A rain crust which formed during the middle of the storm is now down 40-60cm and has become the primary layer of concern during the weekend storm. The early December interface consists of crust, surface hoar, and/or facets and is typically down 70-90cm. Around 20-30cm below this interface is a rain crust from mid-Nov with a thick layer of facets below it. Both the early-Dec and mid-Nov layers have become dormant and are likely being capped at treeline and below by the more recent rain crust layer. However, these layers may still be reactive to heavy triggers such as cornices, explosives, or smaller avalanches stepping down.

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