Avalanche forecast

North Columbia

Dec 27, 2016Avalanche Canada
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Avalanche danger

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

Tuesday's danger ratings are based on about 15cm of new snow. If new snowfall amounts are greater than 20cm in your riding area, the avalanche danger may be High.

Avalanche problems

  • Wind Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Likely - Very Likely
    Size
    1–2
    New snow and wind forecast for Monday night and Tuesday will form new wind slabs in exposed higher elevation terrain.  In the Monashees, where more snow is expected, a more widespread storm slab problem may exist.

  • Persistent Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Possible
    Size
    1–3
    A weak layer buried mid-December now lies up to 75cm below the surface and has the potential for large avalanches. It's a tricky one to manage as it's not a problem in all areas. If in doubt, err on the side of caution and to stick to mellow terrain.

Confidence

Moderate - Forecast snowfall amounts are uncertain on Tuesday

Weather Forecast

Tuesday: 15-25cm of new snow / Strong westerly winds / Freezing level at 500mWednesday: Overcast skies with light flurries / Moderate westerly winds / Freezing level at valley bottomThursday: 5-10cm of new snow / Moderate westerly winds / Freezing level at 500m

Avalanche Summary

A Mountain Information Network post from the Adamant Range on the eastern side of the Selkirks indicated several avalanches failing on the mid-December weak layer. The avalanches were in the size 1-2.5 range and were failing under light loads, in some cases naturally or remotely. A size 2 slab avalanche was also triggered on an alpine slope on Video Peak in Glacier National Park. The avalanche was triggered remotely from a distance of 30 metres. With new snow and strong winds forecast for Monday night and Tuesday, I'd also expect new wind slab activity in higher elevation terrain on Tuesday.

Snowpack Summary

On Tuesday, new snow and wind are forecast to form fresh wind slabs in exposed higher elevation terrain. 40-75 cm of snow now overlies the mid-December interface which consists of a variety of old snow surfaces including wind affected snow, faceted (sugary) crystals, and/or surface hoar crystals. Recent tests suggest the the new snow is well bonded to the interface in most areas. However, this layer is still reactive in some snowpack tests and should be investigated before pushing into steeper terrain. Limited observations suggest this layer has been especially touchy on the eastern side of the Selkirks. The thick mid-November crust layer typically sits 1-2 m down in the snowpack. Recent test results on this layer suggest it is generally well bonded to the adjacent snow with the possible exception of shallow snowpack areas. This layer is considered dormant at this time but remains an isolated concern that we will likely be tracking through much of the season.

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