Avalanche forecast

Purcells

Dec 25 – 26, 2014Avalanche Canada
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Avalanche danger

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

Conservative decision making and terrain use is the name of the game when these tricky avalanche conditions persist. Check out the new Forecaster Blog @ avalanche.ca.

Avalanche problems

  • Persistent Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Likely
    Size
    1–4
    A very touchy surface hoar layer is buried by a 30-70 cm thick persistent slab. This layer is widespread, and is easily triggered by skiers and riders. Remote triggering with wide propagation is a concern.

  • Deep Persistent Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Unlikely - Possible
    Size
    3–6
    A hard rain crust buried 1-1.5 m down seems to be unreactive, however; likely trigger spots are thin rocky and unsupported terrain, or from shallow snowpack areas.

Confidence

Fair - Due to the number of field observations

Weather Forecast

A ridge of high pressure is strengthening a predominant northwesterly flow which will invade the Interior regions. This will bring relatively dry cool air. Ridgetop winds will blow light-moderate from the northwest and alpine temperatures will hover near -15. Skies will likely remain cloudy with some sunny periods Friday and Sunday. Light precipitation is expected Saturday.

Avalanche Summary

On Thursday, explosive controlled size 2.5 occurred and stepped down to the deep persistent early November rain crust. The mid-December buried surface hoar layer remains touchy to skier and rider triggers with several avalanches up to size 1.5 on Wednesday. I don't expect things to improve over the holiday period and suspect this layer is primed for human triggers. Remote triggering up to 100 m is still a concern.

Snowpack Summary

New snow 10-20 cm fell Tuesday night, with southern locations seeing the higher amounts. This brings storm snow totals 30-70 cm above a very touchy surface hoar layer that was buried mid-December. Below 2100 m this slab sits on a thick, solid crust that has been acting as a perfect sliding layer. This persistent slab remains touchy to the weight of a skier and rider, especially in wind effected areas. A hard rain crust with facets from early November is buried over 1 m down and is currently unreactive, however; triggering from shallow rocky and unsupported terrain remains a concern and should be kept on your radar.

Regions covered