Avalanche forecast

North Columbia

Feb 26 – 27, 2020Avalanche Canada
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Avalanche danger

Fri
Sat
Alpine
3 · Considerable
Treeline
2 · Moderate
Below
2 · Moderate
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Highlights

Snow and strong wind are forecast. Riders are starting to be able to trigger slabs over a buried surface hoar layer and the consequence of doing so will only increase as more snowfall accumulates. Conservative decision-making is recommended.

Avalanche problems

  • Storm Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Possible - Likely
    Size
    1–2

    A widespread layer of surface hoar found at all elevations and on all aspects is starting to become reactive to human traffic. The layer is bured around 20 to 40 cm deep and more snow and strong wind will continue to load in on Wednesday. On south aspects, the surface hoar may be found overlying a melt-freeze crust, which is a particularly nasty combination. Travel conservatively and assess this layer before committing to avalanche terrain. Also be aware that snowfall is occurring with strong southwest wind, which will quickly load lee terrain features near ridges.

Confidence

Moderate - Uncertainty is due to how buried persistent weak layers will react with the forecast incoming weather.

Weather Forecast

TUESDAY NIGHT: Cloudy with light snowfall, accumulation 5 to 10 cm, moderate southwest wind, alpine temperature -7 C.

WEDNESDAY: Morning snowfall then cloudy, accumulation 5 to 10 cm, moderate west wind, alpine temperature -8 C, freezing level rising to 1100 m.

THURSDAY: Cloudy with light snowfall, accumulation 2 to 5 cm, light to moderate southwest wind, alpine temperature -6 C, freezing level rising to 1500 m.

FRIDAY: Morning snowfall then a mix of sun and cloud, accumulation 2 to 5 cm, light southwest wind, alpine temperature -5 C, freezing level 1500 m.

Avalanche Summary

Many small (size 1 to 1.5) storm slab avalanches were triggered by skiers on Monday. They occurred at all elevation bands and generally on northwest to east aspects. They were commonly 20 to 30 cm deep and released on the surface hoar layer described in the Snowpack Summary.

Snowpack Summary

Around 20 to 40 cm of snow overlies a widespread layer of surface hoar that was reported to be between 10 and 20 mm in size and at all elevations. This same layer of surface hoar has been reported as sitting on a thin melt-freeze crust on sun-exposed aspects, which is a particularly nasty combination. The new snow will likely become increasingly reactive to human triggers as it stacks up and settles into a cohesive slab.

The early-February melt-freeze crust down 50-100 cm is dormant but should be monitored. The remainder of the mid and lower snowpack is generally well settled and strong.

Terrain and Travel

  • Stick to simple terrain or small features with limited consequence.
  • Watch for newly formed and reactive wind slabs as you transition into wind affected terrain.
  • Avoid terrain traps such as gullies and cliffs where the consequence of any avalanche could be serious.
  • Be aware of the potential for large avalanches due to the presence of buried surface hoar.

Regions covered