Avalanche forecast

South Rockies

Feb 22, 2017Avalanche Canada
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Archived · expired 10 years ago

Avalanche danger

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

Storm slabs may continue to be reactive to human triggers, and deep persistent weak layers continue to be a concern.

Avalanche problems

  • Storm Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Possible - Likely
    Size
    1–2
    Storm slabs may take a couple of days to settle and bond to the old surfaces.

  • Deep Persistent Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Unlikely - Possible
    Size
    2–3
    A weak layer near the base of the snowpack has the potential for large avalanches, especially in areas with minimal rider compaction or thin variable snow cover.

Confidence

Moderate - Due to the number of field observations

Weather Forecast

Tonight: Overcast with a chance of flurries combined with moderate westerly winds and freezing at valley bottoms. Wednesday: Mix of sun and cloud with moderate southwest winds and daytime freezing levels at 1200 metres. Thursday: Temperatures trending colder as the arctic air descends, combined with light southeast winds and 3-5 cm of new snow. Friday: A few more cm of new snow, light winds, and alpine temperatures near -20.

Avalanche Summary

A natural cycle during the storm up to size 1.5 was reported on Tuesday from the Limestone area. Cornice growth was reported to be significant and may have triggered at least one of the storm slabs. Also keep in mind that the deep persistent slab problem is a low probability/high consequence scenario that warrants extra caution around large open slopes, especially in shallow snowpack areas. There was a report today of a size 3.5 avalanche at Mt Harmer in the Lizard/Flathead region that released on or stepped down to the deep weak layer near the ground.

Snowpack Summary

On Limestone ridge today there was 15 cm of new storm snow at 2100 metres elevation. The height of snow on the ground was 160 cm and the foot penetration was 20 cm. The December facets were down 70 cm at this location and produced hard sudden collapse compression test scores in snow profile tests. This elevation is above the extent of the recent rain crust that extends up to about 1900 metres. A deeply buried weak layer of facets (sugary snow) continues to be a concern in most areas of the region. If triggered this deep weak layer may result in very large avalanches down to near the ground.

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