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Avalanche Forecast

Archived

Dec 17th, 2025–Dec 18th, 2025

Alpine
Natural and human triggered avalanches likely.
Treeline
Natural avalanches possible, human triggered probable.
Below Treeline
Natural avalanches possible, human triggered probable.
Alpine
Natural and human triggered avalanches likely.
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.

Mt. Dennis, Mount Bourgeau and Eagle Mountain avalanche closure zones are CLOSED on Thursday, December, 18th.

Confidence

Moderate

  • Uncertainty is due to limitations in the field data.

Avalanche Summary

Avalanche activity continues with two large naturals reported to us today in Kootenay and Yoho. Both were size 3+ and ran to valley bottom.

Sunshine patrol also triggered a size 2.5 with explosives at treeline that ran on a November crust layer and Lake Louise had a couple size 2's in closed areas that failed from rapid wind loading during the day.

Snowpack Summary

With the continued snow and wind 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 is now forming below the recent snow as the temperatures cool from the weekend warmup.

Treeline snowpack depths range from 100-180 cm!!

Weather Summary

A persistent westerly flow continues to bring precipitation to the range. Expect a small reprieve overnight Wednesday followed by 10-15 cm starting Thursday afternoon. Skies will dry up throughout the day on Friday but we can still expect small flurries and another ~ 5 cm on Saturday. Temps will be -5 to -10 at treeline with consistent moderate to strong west and southwest winds throughout the period.

Terrain and Travel Advice

  • Watch for newly formed and reactive wind slabs as you transition into wind-affected terrain.
  • Storm slabs in motion may step down to deeper layers resulting in large avalanches.
  • Continue to make conservative terrain choices while the storm snow settles and stabilizes.

Problems

Storm Slabs

Storm Slab avalanches are the release of a cohesive layer (a slab) of new snow that breaks within new snow or on the old snow surface. Storm-slabs typically last between a few hours and few days (following snowfall). Storm-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.