Avalanche forecast

Kootenay Boundary

Dec 28, 2016Avalanche Canada
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Avalanche danger

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

Recently formed wind slabs are the main concern and are expected to be touchy on Wednesday. Loose dry avalanches are also a concern in steep terrain.

Avalanche problems

  • Wind Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Likely
    Size
    1–2
    Recently formed wind slabs are expected to be reactive to human triggering on Wednesday. Ongoing strong southerly winds have been loading leeward and cross loaded terrain features in wind exposed terrain.

  • Loose Dry

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Likely
    Size
    1–2
    With all the unconsolidated low-density snow that has accumulated, I'd be on the look-out for loose dry avalanches in gullies and other steep features that were sheltered from the wind.

Confidence

Moderate - Wind effect is extremely variable

Weather Forecast

Mostly cloudy conditions are expected on Wednesday with the potential for both light flurries and sunny breaks. Alpine wind is forecast to be moderate to strong from the west to northwest directions. Treeline temperatures are expected to be around -10C. The next storm front is forecast to arrive on Thursday morning. 5-10cm of snowfall is forecast by Thursday evening with another 5-10cm Thursday overnight. Alpine wind is expected to be strong from the southwest and treeline temperatures are forecast to be around -8C. Friday is currently forecast to be dry and sunny.

Avalanche Summary

On Tuesday, numerous natural slab avalanches up to size 2 were reported at treeline in the Whitewater area. Several natural loose dry avalanches up to size 1.5 were also observed on steep southerly aspects at 1700-2100 m elevation in the Kootenay Pass area. Explosives triggered storm slab avalanches up to size 2 at 1800-2100 m elevation which were reported as soft slabs and likely around 30cm thick. On Wednesday, wind slabs are expected to be the main concern. Ongoing strong southerly winds are redistributing the 20-30 cm of new snow from Tuesday. Where the new snow remains unconsolidated, loose dry avalanches from steep terrain are expected to be the main concern.

Snowpack Summary

30-40 cm of low density snow accumulated during the storm on Monday night. The new snow sits over wind scoured surfaces or old wind slabs in exposed terrain and surface hoar up to 5 mm in sheltered areas. In exposed terrain, strong southerly winds have redistributed the new snow and wind slabs exist in leeward terrain features. A freezing rain crust from last week is now down around 60 cm and reports suggest it is generally not creating an instability. The mid-December interface is now down 70-100 cm. While test results suggest it still may be reactive in isolated areas, the layer is generally considered dormant.

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