Avalanche Forecast

Issued: Feb 25th, 2020 4:00PM

The alpine rating is considerable, the treeline rating is moderate, and the below treeline rating is moderate. Known problems include Storm Slabs.

Avalanche Canada mconlan, Avalanche Canada

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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.

Summary

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 cm, moderate southwest wind, alpine temperature -7 C.

WEDNESDAY: Morning snowfall then cloudy, accumulation 2 to 5 cm, moderate west wind, alpine temperature -6 C, freezing level rising to 1400 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 -4 C, freezing level 1600 m.

Avalanche Summary

There were many small to large (size 1 to 2) human triggered storm slabs on Monday. They were generally 20 to 40 cm thick, triggered between 1800 and 2300 m, and occurred on all aspects though mostly northeast to northwest slopes. These avalanches suggest some slopes have enough snow above the surface hoar to produce harmful avalanches.

Snowpack Summary

Around 20 to 40 cm of snow overlies a widespread layer of surface hoar that was reported to be between 5 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 70-100 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.

Problems

Storm Slabs

An icon showing Storm Slabs

Around 20 to 40 cm of snow is sitting on top of a widespread layer of surface hoar found at all elevations and on all aspects, and more snow will slowly accumulate in the coming days. On sun-exposed aspects, the surface hoar is sitting on 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.

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Possible - Likely

Expected Size

1 - 2

Valid until: Feb 26th, 2020 5:00PM

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