Avalanche Forecast

Issued: Feb 24th, 2020 4:00PM

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

Avalanche Canada shorton, Avalanche Canada

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Small storm slab avalanches are easy to trigger at all elevations, so be diligent with choosing low-consequence terrain and avoiding terrain traps.

Summary

Confidence

Moderate - Uncertainty is due to how the snowpack will react to the forecast weather.

Weather Forecast

MONDAY NIGHT: Mostly clear with a few clouds, light wind from the northwest, alpine temperatures drop to -12 C.

TUESDAY: Increasing cloud with some isolated afternoon flurries, light southwest wind, alpine high temperature around -6 C.

WEDNESDAY: Cloudy with scattered flurries and up to 5 cm of new snow, light to moderate southwest wind, alpine high temperature around -2 C with freezing level climbing to 1500 m.

THURSDAY: Cloudy with sunny breaks in the afternoon, light southwest wind, alpine high temperatures around -2 C with freezing level climbing to 1500 m.

Avalanche Summary

Numerous human triggered slabs were reported over the weekend as 20-35 cm of new snow was very reactive above a recently buried surface hoar layer. On Sunday, small (size 1-1.5) soft slab avalanches were triggered on all aspects and elevations. Loose dry avalanches were also widespread. Some of the slabs were remotely triggered and had wide propagations, which are good signs that the new snow is poorly bonded to the surface hoar layer.

Storm slabs above this weak layer will continue to be reactive this week, but the avalanches will be relatively small. The snowpack is setup to be dangerous when the next significant storm arrives.

Snowpack Summary

20-35 cm of recent snow has buried a widespread layer of surface hoar (size 5-20 mm). This layer exists at all elevations. This same layer of surface hoar has been reported as sitting on a thin sun crust on solar 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 rain crust down 70-100 cm. is another prominent layer in the upper snowpack that requires monitoring. The mid and lower snowpack are generally well settled and strong.

Terrain and Travel

  • Carefully assess open slopes and convex rolls where buried surface hoar may be preserved.
  • Choose slopes that are well supported and have limited consequence.
  • Keep your guard up at lower elevations. Storms slabs have been reactive at all elevations.
  • Avoid terrain traps such as gullies and cliffs where the consequence of any avalanche could be serious.

Problems

Storm Slabs

An icon showing Storm Slabs

20-35 cm of recent snow is sitting on top of a widespread layer of surface hoar at all elevations. On solar aspects the surface hoar is sitting on a crust, a particularly nasty combination.

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Possible - Likely

Expected Size

1 - 2

Valid until: Feb 25th, 2020 4:00PM

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