Avalanche forecast

Purcells

Dec 8 – 9, 2012Avalanche Canada
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Avalanche danger

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

Avalanche problems

  • Wind Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Possible - Likely
    Size
    1–4
    Strong winds and storm snow earlier in the week have been responsible for widespread wind slab development. Although they have most likely gained considerable strength, triggering may still be possible in unsupported terrain.

  • Persistent Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Possible - Likely
    Size
    2–5
    Buried surface hoar layers exist in specific locations in the upper metre of the snowpack Rider triggers are likely where this layer sits. Suspect slopes may be sheltered treeline/ below treeline terrain and  most reactive in deeper snowpack areas.

  • Deep Persistent Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Possible
    Size
    1–6
    Recent heavy loading in some areas mean that deep persistent slabs may be primed for triggering. Deep and destructive slides have been reported on this layer in a neighboring region.

Confidence

Fair - Timing of incoming weather is uncertain

Weather Forecast

The Region will be under a cool, windy NW flow through the forecast period.  Light snow amounts expected, with strong NW winds and freezing levels at valley bottom.Sunday: Mainly dry, snow amounts 5-10 cm, ridgetop winds W 20 km/hr switching NW 30-40 km/hr, alpine temps near -7Monday: Trace of new snow, ridgetop winds NW 30-40 km/hr, alpine temps near -8.Tuesday: Light-moderate snow fall amounts, ridgetop winds SW 20 km/hr, alpine temps near -8.

Avalanche Summary

No new avalanche activity reported.

Snowpack Summary

Wind slabs exist in the upper snowpack on north to northeast aspects at treeline and above. Last weeks storm snow and moderate winds have also shaped unseasonably large cornices.Around 80 cm of snow fell over the past week. This loads a surface hoar layer that was buried on November 28th. Although not widespread in the region, releases on this layer may be likely if you have it in your area. A bit deeper (near 100 cm down) another surface hoar layer that developed during mid-November may still exist. Recent testing around the Invermere area has proved this layer to be unreactive. This does not mean its unreactive throughout the region. Its important to dig down in your local riding area, and test these layers before you disregard them. Near the base of the snowpack is the early November crust. Facet sit facets below it, or it may appear as a sandwich of crusts and facets. In some areas it may only now be primed for triggering with recent heavy loading. Observations have been limited; however, deep and destructive slides have been reported on this layer in a neighboring region.

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