Avalanche Forecast

Archived

Dec 25th, 2025–Dec 26th, 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 unlikely, human triggered possible.

Treeline

Natural avalanches unlikely, human triggered possible.

Below Treeline

Natural avalanches unlikely.

Regions

East Purcell, St. Mary.

Assess steep slopes for fresh wind slabs before committing & be mindful that deep instabilities still exist in the snowpack.

Seek out good riding in sheltered terrain with no wind effect.

Confidence

Moderate

Uncertainty is due to the limited number of field observations.

Avalanche Summary

No slab avalanches have been observed in the region since last Saturday.

Looking forward, we expect fresh wind slabs may be triggerable on Friday

If you are travelling in the mountains, please submit any observations to the Mountain Information Network.

Snowpack Summary

10 to 15 cm of snow recently fell in the region, and an additional 5 to 10 cm is expected overnight. The new snow, combined with forecast moderate southwesterly winds, may form wind slabs on lee slopes at upper elevations.

A persistent weak layer from mid-November, made up of a thick crust with overlying facets, and in some cases surface hoar, remains a concern. In eastern parts of the region, it is buried 70–110 cm deep, and up to 180 cm in western areas with a deeper snowpack. In most areas, faceted grains overlie the crust.

Depth hoar is present at the base of the snowpack.

Weather Summary

Thursday Night
Cloudy. 5 to 10 cm of snow, highest amounts for the southern parts of the region. 40 km/h southwest ridgetop wind. Treeline temperature -4 °C. Freezing level 1400 m.

Friday
Cloudy. 0 to 2 cm of snow. 40 km/h southwest ridgetop wind. Treeline temperature -5 °C. Freezing level 1200 m.

Saturday
Mix of sun and clouds. 0 to 5 cm of snow Friday night. 20 km/h northwest ridgetop wind. Treeline temperature -15 °C.

Sunday
Mostly sunny. 20 km/h northwest ridgetop wind. Treeline temperature -16 °C.

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.
Be careful with wind-loaded pockets, especially near ridge crests and rollovers.
In areas where deep persistent slabs may exist, avoid shallow or variable depth snowpacks and slopes above cliffs.

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.