Avalanche forecast

North Rockies

Dec 6 – 8, 2020Avalanche Canada
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Avalanche danger

Tue
Wed
Alpine
2 · Moderate
Treeline
2 · Moderate
Below
1 · Low
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Highlights

  

Expect hazard to be one-step higher in the areas around Pine Pass that received more than 15 cm. of new snow Friday night. 15-25 cm of new snow in the Pine Pass area has formed localized storm slabs reactive to human triggers.

Avalanche problems

  • Wind Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Possible
    Size
    1.5–2.5

    Strong southwest winds have formed deep wind slabs at treeline and alpine elevations on lee and crossloaded slopes. 

  • Storm Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Likely
    Size
    1.5–2.5

      

    15-25 cm of new snow in the Pine Pass area has formed LOCALIZED storm slabs reactive to human triggers. Conservative terrain choices will be especially important in areas that received more than 15 cm. of new snow.

  • Deep Persistent Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Unlikely - Possible
    Size
    2–3

    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.

Confidence

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

Weather Forecast

  

SATURDAY NIGHT: Mostly cloudy with isolated flurries; 0-3 cm. / Strong, southwest ridgetop wind / alpine low temperature -8 / Freezing level 1500 m.

SUNDAY: Cloudy / Strong, southwest ridgetop wind / alpine high temperature -2 / Freezing level 1500 m.

MONDAY: Snow; 15-25 cm. / Strong, southwest ridgetop wind / alpine high temperature -2 / Freezing level 1500 m.

TUESDAY: Mix of sun and cloud / Light, west ridgetop wind / alpine high temperature -3 / Freezing level 1500 m.

Avalanche Summary

The new snow Friday night around Pine Pass is expected to form storm slabs reactive to human triggers.

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.

If you get out into the mountains this weekend, please consider sharing your observations on the Mountain Information Network.

Snowpack Summary

  

A surprise storm Friday night dropped up to 25 cm. of snow in the Pine Pass area which formed fresh storm 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.

Regions covered