Avalanche forecast

South Columbia

Dec 20, 2016Avalanche Canada
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Avalanche danger

Tue
Wed
Alpine
4 · High
Treeline
4 · High
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 stick to simple non-avalanche terrain.

Avalanche problems

  • Loose Dry

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Likely - Very Likely
    Size
    1–2
    Loose dry avalanches from steeper slopes and terrain features may entrain enough mass to bury you.

  • Storm Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Likely - Very Likely
    Size
    1–3
    Heavy storm snow amounts and strong southwest winds continue to build fresh storm slabs. Storm slabs 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 mountains are 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 that will move across the region through the forecast period.Tuesday: Snow 10-20 cm with freezing levels rising to 1000 m. Alpine temperatures -6 and ridgetop winds 35-75 km/hr.Wednesday: Light flurries with freezing levels dropping to valley bottom. Alpine temperatures -11 and ridgetop winds 30-45 km/hr.Thursday: Snow 5-10 cm with alpine temperatures -11. Ridgetop winds 15-35 km/h.

Avalanche Summary

On Monday numerous natural and rider triggered slab avalanches up to size 3 were reported. Given the weather forecast we can expect to see natural avalanche activity continue Tuesday.

Snowpack Summary

Up to 35 cm of storm snow (more to come!) sits over a plethora of old snow surfaces including wind affected snow, faceted (sugary) crystals, surface hoar crystals and a thin sun crust on steep solar aspects. The new snow will likely have a poor bond to these surfaces. Deeper in the snowpack exist two layers that could become reactive through the next series of storms. The first being a spotty surface hoar layer that sits 30-40 cm down and the mid-November crust that sits 100-200 cm down. Recent test results on these layers have varied from moderate and sudden to hard and resistant, and in some cases no result. In shallower snowpack areas faceting is happening below and above the crust. Tracking and monitoring this potentially weak interface is crucial especially while it's being loaded by new snow.

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