Avalanche forecast

Purcells

Jan 7 – 8, 2014Avalanche Canada
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Archived · expired 13 years ago

Avalanche danger

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

Complex avalanche conditions at the moment. The answer to this type of avalanche problem lies in conservative terrain selection. Visit the blog for thoughts on the recent pattern of accidents in the Purcells.

Avalanche problems

  • Persistent Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Unlikely - Possible
    Size
    2–5
    Fresh wind slabs rest on top of two persistent weak layers in the upper meter of the snowpack. Triggering a windslab could add a significant load to the snowpack and possibly step down to a deeper buried persistent weak layer.

  • Deep Persistent Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Possible
    Size
    2–6
    You wouldn't build a house with a weak foundation and you can't trust a snowpack with this kind of structural weakness near the ground. You're most likely to trigger this layer on steep north through east facing slopes with a shallow snowpack.

Confidence

Good

Weather Forecast

Wednesday: A Pacific frontal system starts to affect the interior regions. Cloudy with light snowfall, moderate to strong west winds. Freezing level in the valley bottom.Thursday: Light snowfall, Alpine temperatures -7, moderate west winds.Friday: Light snowfall, alpine temperatures -5, freezing level 1100m, winds moderate west and southwest

Avalanche Summary

There have been a few different close calls with large avalanches in the north of this region in the last two weeks. Check out the incident database for more details. Recent reports from the last 3 days indicate several natural cornice triggered avalanches running to size 3 on east and southeast aspects at treeline and above. Explosives triggered avalanches have continued to be reported to be running to size 2.5 on northerly aspects in the alpine failing on the October facet/crust layer near the base of the snowpack.

Snowpack Summary

Up to 40 cm of recent storm snow lies on top of old wind slabs and a couple of persistent weak layers that exist in the upper meter of the relatively thin snowpack. The mid December surface hoar is buried around 30-90 cm. The early December facet/crust combo is buried down 50-150 cm. Both interfaces give variable results with snowpack tests, but professional operators are treating them with caution.A bigger concern, especially in the Northern part of the region is a layer of weak sugary depth hoar crystals at the base of the snowpack that lie above a crust from early October. Several large avalanches in the last two weeks have been attributed to failures at this layer. Wide propagations on relatively gentle terrain have been noted, as well as a tendency for seemingly disconnected slopes to become connected by one large avalanche.

Regions covered