Avalanche forecast

Purcells

Dec 25 – 26, 2013Avalanche Canada
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Avalanche danger

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

Avalanche problems

  • Wind Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Possible - Likely
    Size
    1–4
    New snow and wind has formed wind slabs over the old dense wind slabs. A small wind slab release may be enough to trigger a deep weak layer, producing a large and destructive avalanche.

  • Deep Persistent Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Possible
    Size
    2–5
    The sensitivity to triggers will likely increase in shallow locations, especially on steep, convex, north-facing slopes.

Confidence

Fair - Timing, track, or intensity of incoming weather system is uncertain on Thursday

Weather Forecast

Thursday: Cloudy with some sunny breaks. Alpine temperatures -2. Ridgetop winds light-moderate from the South. Freezing levels rising to 1600 m.Friday: Snow amounts up to 8 cm. Alpine temperatures near -4. Freezing levels 1000 m.Saturday: Mainly cloudy with isolated flurries, alpine temperatures -9, light westerly winds.

Avalanche Summary

The deep persistent slab problem continues to be reactive up to size 2 with larger triggers such as explosives. Rider triggering is possible especially in shallow snowpack areas like rocky outcrops or near small trees. Additionally on Monday a natural size 2 avalanche was reportedly seen from a NE aspect at 2300 m.

Snowpack Summary

Up to 20 cm of new storm snow covers stiff, dense wind slabs in exposed lee terrain at and above treeline. Average snowpack depths at treeline elevations are 100-130 cm. In the upper 80 cm of the snowpack a couple persistent weak layers exist, comprising of surface hoar and a facet/crust combo. This interface has produced variable results with snowpack tests, and operators are keeping a close eye on them as the load above increases and/or a slab develops.A bigger concern, especially in the Northern part of the region where the snowpack is thinner and more variable is weak faceted and depth hoar crystals combined with a crust from early October. This is now down around 80-120 cm. This deep persistent weakness may be stubborn to trigger, especially in deeper snowpack areas, but the sensitivity to triggers likely increases in shallower locations, especially on steep, convex, north-facing slopes.

Regions covered