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Avalanche Forecast

Archived

Dec 21st, 2025–Dec 22nd, 2025

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

Regions

East Purcell, St. Mary.

Watch for changing conditions as you shift elevation and aspect - wind affected features may remain reactive to human triggers.

Confidence

Moderate

  • Uncertainty is due to the limited number of field observations.
  • Uncertainty is due to the fact that persistent slabs are particularly difficult to forecast.

Avalanche Summary

On Friday, an explosive triggered size 1.5 persistent slab avalanche was reported on a northerly aspect at treeline near Invermere. The slab failed on a crust down 80 to 110 cm.

Several rider-triggered wind slabs up to size 1.5 have occurred in the last 3 days on northerly aspects at treeline.

Snowpack Summary

30–50 cm of recent snow combined with strong southwest winds has formed slabs over a 3–5 cm thick crust, which is present up to approximately 2100 m.

A thick mid-November crust is buried 70–110 cm deep in eastern terrain, and up to 180 cm in areas with a deeper snowpack. In most areas, faceted grains overlie the crust. Specific, sheltered terrain features have surface hoar present on the crust or up to 30 cm above it.

Depth hoar (large, weak crystals) are present at the base of the snowpack.

Weather Summary

Sunday Night
Partly cloudy. 2 to 4 cm of snow. 20 km/h southwest ridgetop wind. Treeline temperature -7 °C. Freezing level 200 m.

Monday
Mix of sun and clouds. 2 to 4 cm of snow. 20 km/h southwest ridgetop wind. Treeline temperature -7 °C. Freezing level 700 m.

Tuesday
Mix of sun and clouds. 1 to 5 cm of snow. 30 km/h southwest ridgetop wind. Treeline temperature -6 °C. Freezing level 400 m.

Wednesday
Mostly cloudy. 5 to 15 cm of snow. 20 km/h south ridgetop wind. Treeline temperature -6 °C. Freezing level 100 m.

More details can be found in the Mountain Weather Forecast.

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.
  • Be mindful that deep instabilities are still present in the snowpack.

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.