Avalanche forecast

Purcells

Dec 5 – 6, 2013Avalanche Canada
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Avalanche danger

Sat
Sun
Alpine
3 · Considerable
Treeline
2 · Moderate
Below
2 · Moderate
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Highlights

Highly variable early-season snowpack conditions exist across the region. Investigate conditions in your local area before heading out.

Avalanche problems

  • Wind Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Possible - Likely
    Size
    2–4
    Recent strong northerly winds have redistributed fresh snow forming hard and soft wind slabs in exposed lee terrain. Windward slopes may be scoured and stripped of snow.

  • Persistent Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Possible
    Size
    2–5
    Recent storm snow overlies a variety of persistent weaknesses including surface hoar and/or a sun crust. It seems to be more of a concern in the southern part of the region where it is up to 70 cm deep.

  • Deep Persistent Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Unlikely
    Size
    2–5
    A weak crust/facet layer near the base of the snowpack has the potential to create large, destructive avalanches. This is primarily a concern in shallow snowpack areas but may also be a problem on unsupported or convex slopes.

Confidence

Fair - The weather pattern is stable

Weather Forecast

Synopsis: The Arctic ridge of high pressure will continue to dominate the weather pattern through the weekend. Mainly sunny skies and cold temperatures are forecast. Alpine temperatures should hover between -20 to -25, maybe even approaching -30. Winds are generally light to moderate from the north, with stronger northwest winds forecast for Sunday.

Avalanche Summary

We are still receiving limited reports. Explosive control on Tuesday produced numerous avalanches to size 2, primarily on north aspects. Recent snowpack tests suggest the continued potential for human triggered avalanches, particulary in exposed wind-loaded terrain. If you have seen any recent avalanche activity, please send your reports to [email protected].

Snowpack Summary

Snowpack depth varies greatly across the region, averaging 70-110cm at treeline. The southern portion of the region received substantially more new snow (up to 70cm ) compared to the northern portion (as little as 10cm). The recent storm snow is sitting on top of the late-November interface which may consist of surface hoar on sheltered/shaded slopes, a melt-freeze crust on south facing slopes, or a combination of both in isolated locations. Strong NE winds after the storm have caused reverse loading and wind slab formation on SE through W aspects in wind exposed areas. In the southern part of the region there is 40-70cm of new snow over the late-November interface which has created a persistent slab problem. The current cold temperatures will contribute to the persistence of the late-November weak layer. In the northern part of the region the lower/mid snowpack is fundamentally weak, composed of an early season crust (more prevalent on north aspects) and weak faceted crystals. While many areas did not receive enough new snow to create a new slab problem on top of the late-November interface, there are likely isolated areas where a persistent slab does exist.

Regions covered