Avalanche forecast

Purcells

Dec 20, 2016Avalanche Canada
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Avalanche danger

Tue
Wed
Alpine
4 · High
Treeline
3 · Considerable
Below
3 · Considerable
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Highlights

More snow, strong winds and warmer temperatures are driving the danger ratings. It's a good time to make conservative choices and stick to simple terrain.

Avalanche problems

  • Loose Dry

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Likely
    Size
    1–2
    Loose dry avalanches/ sluffing are likely from steeper slopes and terrain features.

  • Storm Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Likely
    Size
    1–3
    New snow and strong winds will continue to build fresh storm slabs. They are reactive due to the poor bond with the old snow surfaces.

Confidence

Moderate - Forecast snowfall amounts are uncertain on Tuesday

Weather Forecast

The Interior is under a strong zonal flow that is responsible for pushing out the cold air and bringing in the snow! We can expect to see an additional two - three systems move across the region through the forecast period.Tuesday: Snow 8-15 cm with freezing levels rising to 1000 m. Alpine temperatures -9 and ridgetop winds 35-60 km/hr.Wednesday: Snow 5 cm with freezing levels dropping to valley bottom. Alpine temperatures -11 and ridgetop winds 30-55 km/hr.Thursday: Snow 5-10 cm with alpine temperatures -9. Ridgetop winds 15-35 km/h.

Avalanche Summary

Loose snow and wind slab avalanches up to size 2 were reported on Monday. Given the weather forecast we can expect to see avalanche activity on Tuesday.

Snowpack Summary

Up to 15 cm of storm snow sits over a plethora of old snow surfaces including stiff wind affected snow, faceted (sugary) crystals and surface hoar crystals that formed in locations sheltered from the wind. The new snow will likely have a poor bond to these surfaces. 20-40 cm below this new snow sits an older buried surface hoar layer, reported from the Dogtooth Range. This layer may me reactive with additional load. The mid-November crust is buried down around 70-90 cm and test results have been variable from sudden failures to no results. In shallower snowpack areas reports indicate that the bond to the crust is weakening. Tracking and monitoring this potentially weak interface is crucial especially as we move forward into this snowy period where the snowpack will see more load.

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