Avalanche forecast

South Rockies

Dec 15 – 16, 2015Avalanche Canada
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Avalanche danger

Thu
Fri
Alpine
2 · Moderate
Treeline
2 · Moderate
Below
1 · Low
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Highlights

Wind slabs may exist on several aspects in the alpine and at treeline. Light additional loads like a single skier may be enough to trigger these weak pockets.

Avalanche problems

  • Wind Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Possible
    Size
    1–2
    Pockets of wind slab may be found on several aspects in the alpine and at treeline due to changing wind directions and loose snow available for transport.

  • 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.

Avalanche Summary

On Monday, a couple of size 2 avalanches were reportedly triggered by skiers in steep north and northeast facing slopes. Over the weekend, explosives and ski cutting produced storm slabs size 1-2 which were typically 20-60cm thick.

Weather Forecast

Light to moderate winds overnight combine with 5-10 cm of new snow and alpine temperatures around -18. Clearing trend on Wednesday should provide broken skies at least by the afternoon. Clear and cold overnight with cloud and strong southwest winds developing on Thursday. The next Pacific moisture should move into the region by Friday.

Confidence

Moderate - Track of incoming weather systems is uncertain on Friday

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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