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Avalanche Forecast

Archived

Dec 20th, 2025–Dec 21st, 2025

Alpine
Natural avalanches possible, human triggered probable.
Treeline
Natural avalanches possible, human triggered probable.
Below Treeline
Natural avalanches unlikely, human triggered possible.
Alpine
Natural avalanches possible, human triggered probable.
Treeline
Natural avalanches possible, human triggered probable.
Below Treeline
Natural avalanches unlikely, human triggered possible.
Alpine
Natural avalanches possible, human triggered probable.
Treeline
Natural avalanches unlikely, human triggered possible.
Below Treeline
Natural avalanches unlikely, human triggered possible.

Regions

Banff Yoho Kootenay, Little Yoho, Banff, East Side 93N, Kootenay, Lake Louise, LLSA, Sunshine, West Side 93N, Field.

Although the recent natural avalanche cycle has ended, explosive control continues to produce large avalanches that run to mid runout. The snowpack need time to adjust to the 100-140 cm storm snow load that it has received since early December. Avoid the temptation to jump into bigger terrain, there is great skiing in the trees.

Confidence

Avalanche Summary

Highway avalanche control in Yoho and Sunshine on Dec 18 and 19 produced results in the 2.5-3 range.

Lake Louise skihill reported several explosive triggered wind slabs up to 1.5.

Sunshine reported one size 3 persistent slab in previously uncontrolled terrain and one size 2.5 windslab.

Snowpack Summary

There has been 5-15 cm of new snow since Friday and recent mod to strong SW winds have produced fresh wind slabs in alpine and treeline elevations. There is 35-50 cm of settled storm snow over top of the Dec 15 melt freeze crust (which rises to 2000m).

The mid Nov crust interface is down 80-140 cm and was active this week with numerous large natural and explosive controlled avalanches.

Treeline snow depths are around 100-180 cm.

Weather Summary

Light flurries continue through Saturday night and Sunday with total accumulations along the Divide up to 10 cm. Moderate SW winds and treeline temperatures around -8C forecasted for Sunday.

Link to updated weather forecast tables from Environment Canada.

Terrain and Travel Advice

  • 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.

Problems

Wind Slabs

Wind Slab avalanches are the release of a cohesive layer of snow (a slab) formed by the wind. Wind typically transports snow from the upwind sides of terrain features and deposits snow on the downwind side. Wind slabs are often smooth and rounded and sometimes sound hollow, and can range from soft to hard. Wind slabs that form over a persistent weak layer (surface hoar, depth hoar, or near-surface facets) may be termed Persistent Slabs or may develop into Persistent Slabs.

Persistent Slabs

Persistent Slab avalanches are the release of a cohesive layer of snow (a slab) in the middle to upper snowpack, when the bond to an underlying persistent weak layer breaks. Persistent layers include: surface hoar, depth hoar, near-surface facets, or faceted snow. Persistent weak layers can continue to produce avalanches for days, weeks or even months, making them especially dangerous and tricky. As additional snow and wind events build a thicker slab on top of the persistent weak layer, this avalanche problem may develop into a Deep Persistent Slab.