Avalanche Forecast

Archived

Dec 30th, 2024–Dec 31st, 2024

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

Purcells, Crawford, Dogtooth, East Purcell, Moyie, St. Mary, West Purcell.

A calm weather day marks the end of the year.

Uncertainty remains around the reactivity of deeper weak layers.

Continue to avoid rocky, wind-affected areas where triggering is possible.

Confidence

Moderate

Avalanche Summary

On Sunday, skiers accidentally triggered a small storm slab (size 1) on a southeast alpine feature near Panorama. Several natural small loose avalanches were also reported from steep terrain., some induced by solar radiation.

In the Bugaboos, large wind slabs (size 2) were triggered by cornice falls on northerly alpine slopes.

If you head out in the backcountry, let us know what you are seeing by submitting a MIN report!

Snowpack Summary

In sheltered areas, 15 to 30 cm of recent snow can be found. The previous southwest wind has redistributed this snow, forming deeper deposits on leeward slopes at higher elevations. Surface snow consists of surface hoar crystals and facets on northerly slopes and a thin sun crust on southerly slopes.

A weak layer buried in early December is now about 40 to 90 cm below the surface. This layer varies between weak surface hoar or facetted crystals on shaded slopes and a sun crust with facets on south-facing slopes. Professionals are still concerned about its potential instability.

The base of the snowpack is made of a thick crust and facets in many areas.

Weather Summary

Monday Night

Partly cloudy, with isolated flurries. 10 to 20 km/h west ridgetop wind. Treeline temperature -12 °C.

Tuesday

Partly cloudy, with isolated flurries. 10 to 20 km/h southwest ridgetop wind. Treeline temperature -12 °C.

Wednesday

Partly cloudy, with isolated flurries. 10 to 20 km/h southwest ridgetop wind. Treeline temperature -14 °C.

Thursday

Partly cloudy, with isolated flurries. 20 to 30 km/h southwest ridgetop wind. Treeline temperature -14 °C.

More details can be found in the Mountain Weather Forecast.

Terrain and Travel Advice

Avoid shallow snowpack areas, rocky outcrops, and steep terrain where triggering is most likely.
Be especially cautious as you transition into wind-affected terrain.
If triggered, wind slabs avalanches may step down to deeper layers resulting in larger avalanches.
Pay attention to the wind; once it starts to blow, sensitive wind slabs are likely to form.

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.