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Avalanche Forecast

Archived

Dec 19th, 2025–Dec 20th, 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 possible, human triggered probable.
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.

Multiple large natural and explosive controlled avalanches have occurred since Wednesday and some have ran into below treeline terrain. Continued moderate to strong winds with light flurries will keep the hazard elevated for Saturday. Cautious route finding and conservative decision-making are essential for this weekend.

Confidence

Avalanche Summary

On December 19th avalanche control was conducted on Mt Stephen, Field, Bosworth, and Cathedral that achieved results up to size 3, but generally to size 2.5, some of the terrain had been previously controlled. Ski hills reported some explosive results, and a skier remote up to size 2 involving the persistent or wind slabs.

Avalanche control on December 18th on Mt Dennis and on the Sunshine access road produced similar results to size 3 where avalanches ran to 3/4 runout.

Snowpack Summary

With the continued wind and snow over the past week, there is now a 50 -100 cm+ slab overlying the November crust / facet layers. These layers have been active this week with avalanches up to size 3.5, occasionally scrubbing to ground.

Below 2100m, a new crust has formed below the recent snow as the temperatures cool from the weekend warmup.

Treeline snowpack depths range from 100-180 cm!!

Weather Summary

Light flurries Friday night (2-10 cm) and flurries through Saturday (10 cm). Moderate west winds overnight, increasing to strong SW winds on Saturday. Treeline temperatures will be around -12C overnight and Saturday. Another system is forecast for Sunday-Monday, but snow amounts are uncertain at this time.

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

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.

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.