Avalanche Forecast

Issued: Dec 7th, 2020 4:00PM

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

Avalanche Canada JSmith, Avalanche Canada

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10-15 cm. of new snow and strong southerly winds Monday night will form fresh wind slabs reactive to human triggers. These wind slabs could step-down to deeper weak layers, resulting in very large avalanches.

Summary

Confidence

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

Weather Forecast

  

MONDAY NIGHT: Snow; 10-15 cm. / Strong, south ridgetop wind / alpine low temperature -5 / Freezing level 1000 m.

TUESDAY: Snow; 5-10 cm. / Moderate, southwest ridgetop wind / alpine high temperature -3 / Freezing level 1200 m.

WEDNESDAY: Mostly cloudy / Moderate, west ridgetop wind / alpine high temperature -6 / Freezing level valley bottom.

THURSDAY: Mix of sun and cloud / Light, southwest ridgetop wind / alpine high temperature -7 / Freezing level valley bottom.

Avalanche Summary

10-15 cm of new snow Monday night and strong southerly winds are expected to form fresh wind slabs reactive to human triggers at treeline and above.  

There was an avalanche fatality near Pine Pass on Saturday, November 28. Reports indicate a size 3 deep persistent slab avalanche at approximately 1600 m elevation on a northeast aspect. The avalanche was approximately 55 cm deep, 800 m wide and ran 400 m in length. The avalanche may have run on a weak layer of faceted crystals sitting on a crust that was buried in early November.

Observations in this region are very limited, please post your observations to the Mountain Information Network.

Snowpack Summary

10-15 cm of new snow Monday night and strong southerly winds are expected to form fresh wind slabs reactive to human triggers at treeline and above.  

The snowpack is highly variable due to recent strong southwest winds. In some areas, the windward slopes have been stripped of any recent snow. On lee aspects, wind deposited snow drifts may be up to 90 cm deep. Fresh wind slabs may be reactive to human triggers.

  A crust that was buried in early November is near the base of the snowpack. In some areas, weak, sugary facets are sitting on this crust. It is most likely to be reactive to human triggers on south facing slopes and on steep, shallow, rocky, snowpack areas in the alpine.

Snow depths are approximately 150 cm in the northwest of the region (Pine Pass), 180 cm in the south (Renshaw, Kakwa) and 100 cm in the the northeast (Tumbler ridge). 

Terrain and Travel

  • Watch for newly formed and reactive wind slabs as you transition into wind affected terrain.
  • Closely monitor how the new snow is bonding to the crust.
  • If triggered, wind slabs avalanches may step down to deeper layers resulting in larger avalanches.
  • Avoid steep convexities or areas with a thin, rocky, or variable snowpack.
  • Avoid lee and cross-loaded terrain.

Problems

Wind Slabs

An icon showing Wind Slabs

10-15 cm of new snow Monday night and strong southerly winds are expected to form fresh wind slabs reactive to human triggers at treeline and above.  

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

Elevations: Alpine, Treeline.

Likelihood

Likely

Expected Size

1 - 2

Deep Persistent Slabs

An icon showing Deep Persistent Slabs

There is currently 90-120 cm of snow sitting on top of weak a layer of sugary facets that developed above a crust which formed in early November. It is most likely to be reactive to human triggers on south facing slopes and on steep, shallow, rocky, snowpack areas in the alpine.

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Unlikely - Possible

Expected Size

2 - 3

Valid until: Dec 9th, 2020 4:00PM