Avalanche forecast

Purcells

Dec 12 – 13, 2014Avalanche Canada
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Avalanche danger

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

Although the trend shows improvement  the potential for triggering an avalanche is greatest at higher elevations due to recent heavy snowfall and strong winds.

Avalanche problems

  • Persistent Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Unlikely - Possible
    Size
    2–5
    The likelihood of triggering a persistent slab should decrease heading into the weekend but be wary of any slope that did not release during the storms or has been reloaded.

  • Storm Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Possible
    Size
    1–4
    Use caution in the alpine where most of the recent precipitation has fallen as snow. Watch for wind loaded or cross loaded slopes well below ridge crests from the past week of strong southerly winds.

Confidence

Good

Weather Forecast

A ridge of high pressure will build over BC resulting in much drier and cooler weather for the next few days. Most areas should see a mix of sun and cloud with slight chance of the odd flurry. Freezing levels should gradually drop to 500-1000 m on Saturday and to valley bottom for Sunday and Monday. Winds ease off and become light and variable.

Avalanche Summary

Recent observations are limited from the region but there was a report of a size 2.5 explosive controlled wind slab on Thursday. This slide likely failed on weak layer buried in early December but appeared to step down to the early November crust. On Wednesday, one observer from the McMurdo Hut southwest of Golden reported seeing numerous avalanche crown lines and significant debris, particularly from alpine terrain. Natural activity should taper off this weekend but there may be lingering potential for triggering fresh wind or storm slabs higher in the alpine.

Snowpack Summary

The snow surface likely consists of moist/wet snow or a melt-freeze crust up to 2000-2200 m. Above this elevation there could be up to 40 cm of dense storm snow, which has probably been blasted around by strong southerly winds. In the Golden area a weak layer of surface hoar or facetted snow can be found under the storm snow. The mid pack consists of settled snow, facets, and melt-freeze crusts (primarily lower elevations). The mid-November weak layer (surface hoar, facets, and/or a crust) is buried 60-80 cm deep. Below this you will likely find a thick layer of sugary facets sitting on a solid rain crust from early November. The early November crust/facet layer did become reactive near Golden this week.

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