Avalanche forecast

Purcells

Dec 12 – 13, 2013Avalanche Canada
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Archived · expired 13 years ago

Avalanche danger

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

Avalanche problems

  • Wind Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Possible - Likely
    Size
    1–3
    Shifting winds have redistributed snow, forming wind slabs in lee terrain that may be more reactive above a weak layer. Recent new snow may have a poor bond to old surfaces causing loose dry avalanches from steep, sheltered terrain.

  • Persistent Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Unlikely - Possible
    Size
    2–5
    In deeper snowpack areas, it may be possible to trigger an avalanche on a layer of buried surface hoar. In shallower ones, watch for a weak sugary facet layer near the base. The most likely place to trigger them is on steep, convex slopes.

Confidence

Fair - Intensity of incoming weather systems is uncertain on Saturday

Weather Forecast

Friday shows a lull between systems. The Interior will be mainly dry, especially further south. By Saturday another pacific frontal system will spread light-moderate amounts of precipitation accompanied by strong westerly ridgetop winds. Friday: Cloudy with snow amounts 3-5 cm. Alpine temperatures near -9. Ridgetop winds strong from the West. Saturday: Cloudy with snow amounts 5-10 cm. Alpine temperatures -8. Ridgetop winds strong from the West.Sunday: Cloudy with snow amounts near 10 cm. Alpine temperatures -7. Ridgetop winds moderate from the SW.

Avalanche Summary

No recent avalanche activity has been reported. On Tuesday, a wind slab avalanche size 1.5 was easily triggered under the weight of a rider from a NE aspects. Cross-loaded features and the immediate leeward side of ridge crests are likely touchy. Loose dry surface sluffing from steeper terrain is expected, use caution near terrain traps like cliffs, and depressions.

Snowpack Summary

Shifting winds have formed stiff wind slabs on the lee side of ridge lines.Snowpack depths at treeline vary across the region, averaging 70-110 cm. Incremental snowfall amounts are burying surface hoar and a faceted upper snowpack. In the Southern part of the region there is 40-70cm of low density snow sits over the late-November surface hoar/ crust/ facet interface. This layer may become reactive with additional load, and warming temperatures, forming more of a slab.In the Northern part of the region the lower/mid snowpack is weak, composed of an early season crust (more prevalent on north aspects) weak faceted crystals and depth hoar above and below the crust. This persistent slab may be stubborn to trigger, but if triggered have high consequences.

Regions covered