Avalanche Forecast

Issued: Nov 28th, 2021 4:00PM

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

Avalanche Canada jleblanc, Avalanche Canada

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Current conditions are challenging and require slope by slope evaluation. If in doubt, choose simple terrain. 

Summary

Confidence

Low - Uncertainty is due to the limited number of field observations.

Weather Forecast

The snow will taper off as outflow winds push drier and colder air across White Pass as the Arctic front finally moves further south. Flurries will be on and off until the next significant snowfall late Tuesday.

SUNDAY NIGHT: Snow 5-10 cm / Strong, southwesterly winds / Low of -12

MONDAY: Cloudy with flurries, 3-5 cm / Strong, southerly winds / High of -10

TUESDAY: Cloudy with flurries; 3-5 cm / Moderate, southerly winds / High of -10

WEDNESDAY: Snow 10-15 cm / Strong, southwesterly winds / High of -8

Avalanche Summary

Few natural avalanches (size 1) were observed on cross-loaded features at treeline on Saturday near Powder Valley after the recent strong winds formed reactive slabs. Deeper in the snowpack, a weak layer combining facets and crusts has also produced isolated, but surprisingly large avalanches. 

If you go out in the mountains, please post your observations and/or photos to the Mountain Information Network!

With uncertainty about the snowpack structure, it may also be possible to trigger large avalanches from thin areas on big alpine slopes. Until there is more information about the snowpack, an extra-cautious approach and careful snowpack evaluation is recommended, especially in high-consequence terrain.

 

Snowpack Summary

30+ cm of recent storm snow and strong southwesterly winds have formed thick wind slabs reactive to human triggers.

A persistent weak layer of facets over a crust near the bottom of the snowpack has been reported as being reactive to human triggers near Fraser. Read about it in the Mountain Information network HERE.

Terrain and Travel

  • Avoid freshly wind loaded terrain features.
  • Use ridges or ribs to avoid areas of wind loaded snow.
  • Be aware of the potential for large avalanches due to the presence of a persistent slab.
  • Watch for signs of instability like whumpfing, hollow sounds, shooting cracks or recent avalanches.
  • Avoid shallow snowpack areas, rock outcroppings and steep convex terrain where triggering is most likely.

Problems

Wind Slabs

An icon showing Wind Slabs

30+cm of recent storm snow and strong southwesterly winds have formed thick wind slabs reactive to human triggers. Additional amounts of snow and more wind transport are expected over the next days, maintaining the likelihood triggering wind slabs.

Aspects: North, North East, East, North West.

Elevations: Alpine, Treeline.

Likelihood

Likely

Expected Size

1.5 - 2.5

Persistent Slabs

An icon showing Persistent Slabs

A persistent weak layer of facets over a crust near the bottom of the snowpack has been reported as being reactive to human triggers near Fraser. Read the Mountain Information Network report HERE.

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Possible

Expected Size

2 - 3

Valid until: Nov 29th, 2021 4:00PM