Avalanche forecast

South Rockies

Jan 19, 2017Avalanche Canada
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Avalanche danger

Thu
Fri
Alpine
3 · Considerable
Treeline
3 · Considerable
Below
2 · Moderate
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Highlights

The shallow weak snowpack continues to be a concern for triggering large avalanches.

Avalanche problems

  • Wind Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Possible
    Size
    1–2
    Although there's not much new snow in the forecast, strong winds will transport loose surface snow and form touchy wind slabs on lee features.

  • Persistent Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Possible
    Size
    2–3
    Rapid warming will increase the likelihood of triggering persistent weak layers that have been lingering deep in the snowpack.

Confidence

Moderate - Due to the number of field observations

Weather Forecast

Strong southwest winds and 2-3 cm of new snow expected overnight with freezing levels dropping to about 1200 metres by morning. Overcast with moderate southwest winds and 2-3 cm of new snow during the day on Thursday as the freezing levels rise to about 1400 metres. Clearing and cooler with light winds on Friday and freezing levels at valley bottom by morning. Mostly clear on Saturday with light winds and temperatures near -10 in the alpine.

Avalanche Summary

No new avalanches reported. We continue to be concerned for triggering the weak facetted layers in the snowpack, and our uncertainty revolves around what type of loading or weak spots are required for human triggering.

Snowpack Summary

Recent widespread wind affect in exposed alpine and treeline terrain has formed reactive wind slabs on lee features. The mid pack is quite variable throughout the region and the structure depends on snow depth. In deeper snowpack areas, the snowpack appears to be well settled and right side up with isolated concerns for the mid-December facet layer found 50 to 80 cm deep. In shallow snowpack areas and lower elevations, the snowpack is heavily faceted and there are concerns for the mid-December weak facet layer as well as weak basal facets. If a persistent slab is triggered from thinner snowpack areas it may release on the basal facets resulting in a full depth avalanche. Triggering these deeper weak layers will become more likely this week as warm temperatures soften the overlying slab.

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