Avalanche forecast

North Rockies

Dec 5 – 6, 2020Avalanche Canada
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Avalanche danger

Mon
Tue
Alpine
3 · Considerable
Treeline
3 · Considerable
Below
2 · Moderate
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Highlights

It's going to be HOT! Sunny skies, 3500 m freezing levels, and alpine temperatures up to +5 are in the cards for Saturday. Choose low angle terrain on all aspects, especially on sun exposed slopes. 

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. These wind slabs may become more reactive as temperatures rise.

  • Loose Wet

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Likely
    Size
    1–2

    Wet loose avalanches will become increasingly likely as temperatures rise and the sun hits the 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 crust which formed in early November. Warm temperatures may increase the likelihood triggering deep persistent slabs.

Confidence

Low - Uncertainty is due to limitations in the field data. Uncertainty is due to the timing or intensity of solar radiation and its effect on the snowpack.

Terrain and Travel

  • Avoid sun exposed slopes, especially if snow surface is moist or wet.
  • Watch for newly formed and reactive wind slabs as you transition into wind affected terrain.
  • 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.

Weather Forecast

Unseasonably warm temperatures are expected to continue through the weekend, with some snow in the forecast for Monday

FRIDAY NIGHT - Mainly cloudy with scattered flurries / southwest wind, 60-80 km/h / alpine low temperature near -1 / freezing level 2000 m

SATURDAY - Mainly sunny, possible valley cloud / southwest wind, 60-80 km/h / alpine high temperature near +5 / freezing level 3500 m

SUNDAY - A mix of sun and cloud with isolated flurries / southwest wind, 40-50 km/h / alpine high temperature near +1 / freezing level 2300 m

MONDAY - Flurries, 5-10 cm / southwest wind, 50-70 km/h / alpine high temperature near 0 / freezing level 1800 m

Avalanche Summary

Warm temperatures and sunny skies in the alpine on Saturday could cause an increase in avalanche activity. Pay special attention to the temperature, as avalanches will be more likely on all aspects with significant warming.

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

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. This layer is of most concern on steep terrain in thin snowpack areas.

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).  

Regions covered