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Avalanche Forecast

Archived

Dec 12th, 2025–Dec 13th, 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.

Avalanche control work on Thursday triggered slabs up to size 3 and flights found a natural cycle up to sz 3.5.

While natural activity has tapered off, the potential for human triggering remains.

Expect Avalanche Hazard to remain elevated through the weekend as the winds pick up and temperatures rise.

Confidence

Moderate

Avalanche Summary

Thursday, explosive avalanche control on Mounts Whymper and Field produced many sz 2.5 and a few sz 3 avalanches. Crowns averaged 60-80cm but were up to 100cm deep with most failing midpack on the November 22 interface.

Flights found evidence of a widespread avalanche cycle with many events exceeding sz 3. Significant naturals included a sz 2.5 over the ice on Bourgeau Left-Hand and a sz 3.5 on the Whymper South route that took almost all of the snow from all slopes in the basin.

Snowpack Summary

30-60cm of storm snow arrived this week with strong SW winds. Fresh wind slabs are prevalent in the alpine and into treeline up to 60cm deep. 60-80cm of snow sits over a mid-November interface of facets that are particularly touchy when they are associated with a sun or temperature crust that exists in some places well into the alpine. Further down, the November 13 rain crust extends to 2100-2300m.

Weather Summary

Treeline temperatures are expected to remain near -5C Saturday morning with west winds shifting SW and increasing to strong in the alpine. Trace amounts of precip as temperatures climb above freezing at 2000m.

An above-freezing layer is forecast to keep 2000m temperatures near zero overnight Saturday with light precip expected Sunday.

For more info, click here for Environment Canada tables.

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.

Loose Dry

Loose Dry avalanches are the release of dry unconsolidated snow and typically occur within layers of soft snow near the surface of the snowpack. These avalanches start at a point and entrain snow as they move downhill, forming a fan-shaped avalanche. Other names for loose-dry avalanches include point-release avalanches or sluffs.