Avalanche forecast

South Rockies

Dec 20 – 21, 2020Avalanche Canada
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Avalanche danger

Tue
Wed
Alpine
3 · Considerable
Treeline
2 · Moderate
Below
1 · Low

Highlights

Wind slabs in open areas may still be reactive. More sheltered treeline terrain will likely provide better riding quality.

Avalanche problems

  • Wind Slabs

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

    Incremental snowfall amounts, strong westerly wind and rising temperatures are forecast for Sunday. Use caution near ridges and avoid leeward slopes, particularly where you find stiff wind affected snow. 

  • Persistent Slabs

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

    30-50 cm of snow currently sits above a buried crust from early December. Sugary, facets above and/or below the crust may weaken the bond and the persistent slab may become reactive, especially to human triggers. 

Confidence

Moderate - Uncertainty is due to limitations in the field data.

Weather Forecast

SATURDAY NIGHT - Trace to 5 cm / west wind, 40-80 km/h / alpine low temperature near -9 / freezing level at 1400

SUNDAY - A mix of sun and cloud/ trace to 5 cm / west wind, 40 km-90 km/h / alpine high temperature near -5 / freezing level 1800 m

MONDAY - 8-15 cm / southwest wind, 30-40 km/h gusting to 75 km/h / alpine high temperature near 0 / freezing level 1800 m 

TUESDAY - 15-20 cm / northeast wind 15-40 km/h / freezing level 1700m

Avalanche Summary

On Saturday a natural size 2.5 avalanche was spotted out of extreme, shallow, rocky, wind affected terrain in the Crowsnest Pass. It was thin, but propagated widely. The date of the event was uncertain.

There were a few reports of both natural and explosives triggered avalanches up to size 2 on Thursday and Friday. 

Please consider sharing your observations on the Mountain Information Network. Thank you to those that have already submitted this winter!

Snowpack Summary

Recent incremental snowfalls and strong to extreme southwest wind have likely formed reactive wind slabs at treeline and in the alpine.

This recent snow means there is now 30-50 cm above the early December crust which exists up to approximately 2000 m. Use caution if you find cohesive snow above this crust; there may be weak faceted grains above or below the crust. 

The base of the snowpack consists of a hard melt-freeze crust from early-November that may have faceted grains around it. There has not been recent avalanche activity on this layer but it remains on our radar. The most likely spot to trigger it would be on thin and rocky slopes.

Snowpack depths vary substantially in the region with the average snowpack depth at treeline being approximately 100 cm.

Terrain and Travel

  • 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 areas where the snow feels stiff and/or slabby.

Regions covered