Avalanche forecast

Purcells

Feb 21 – 22, 2016Avalanche Canada
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Avalanche danger

Tue
Wed
Alpine
3 · Considerable
Treeline
3 · Considerable
Below
2 · Moderate
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Highlights

There is potential to trigger very large and dangerous avalanches, especially in the Northern part of the Purcells. Conservative terrain choices are essential.

Avalanche problems

  • Cornices

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Possible
    Size
    1–4
    Natural cornice falls may trigger storm slab avalanches on the slopes below. Periods of strong solar radiation may increase the likelihood of natural cornice falls.

  • Persistent Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Likely
    Size
    1–4
    It may be possible to trigger weaknesses within the recent storm snow or at the crust interface at the bottom. be particularly cautious in wind-loaded and cross-loaded terrain near ridge crests.

  • Deep Persistent Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Unlikely - Possible
    Size
    3–6
    The early January surface hoar may continue to be triggered by large loads like storm snow avalanches in motion, or light loads in shallow or weak spots on large terrain features. This problem is more likely in the north of the region near Golden.

Confidence

Moderate

Weather Forecast

Monday: Cloudy with flurries in the morning and sunny breaks in the afternoon. The freezing level is around 1500 m and ridge winds are light from the NW. Tuesday: Mainly sunny. The freezing level is around 1500 m and ridge winds are light from the W-SW. Wednesday: Mainly sunny. The freezing level is around 1600 m and ridge winds are light to moderate from the W-SW.

Avalanche Summary

On Saturday one person was killed and another was hospitalized in a large avalanche in the Quartz Creek area west of Golden. This size 3 snowmobile-triggered slab avalanche occurred on a S-SW aspect in the alpine and is suspected to have released on the Feb. 12 interface. Explosive control in other areas produced a few slabs, cornice falls, and loose dry slides up to size 2. Natural wind slab avalanches up to size 2.0 were reported on Friday, as well as skier accidental storm slabs to size 1.5.

Snowpack Summary

20-30 cm of snow in the past few days has added to the recent storm slab above the buried crust buried about 40-60 cm below the surface. This melt freeze crust likely exists in most places except for in high elevation shaded terrain. In general there seems to be a reasonable bond between the crust and the overlying snow. I'd still keep an eye on this interface as it has become reactive on some features. Periods of strong solar radiation may increase the likelihood of triggering the storm slab. In isolated areas there may be a weak layer of surface hoar at the storm snow/crust interface that is touchy to human triggers and may result in wide propagations. The early January surface hoar/ facet layer is typically down 70-120 cm. Avalanche activity at this interface has tapered-off over the past week, but I'd be reluctant to trust this potentially destructive layer just yet. In general, the lower snowpack is well settled and strong, apart from some thin snowpack areas where basal facets exist.

Regions covered