Avalanche Forecast

Archived

Dec 30th, 2023–Dec 31st, 2023

Alpine

Natural avalanches possible, human triggered probable.

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.

Alpine

Natural avalanches unlikely, human triggered possible.

Treeline

Natural avalanches unlikely, human triggered possible.

Below Treeline

Natural avalanches unlikely.

Regions

Purcells, Dogtooth, East Purcell, West Purcell.

A complex snowpack situation with multiple deep instabilities is best managed through conservative terrain selection.

Confidence

Moderate

Avalanche Summary

Avalanche observations from the alpine in the past three days;

explosive-triggered persistent layers stepping down to the ground and up to size 2 in the Dogtooth range
explosive-triggered wind slabs, size 1.5 in the northwest Purcells
ski cut loose dry to size 1 in the upper snowpack facets near Invermere

Snowpack Summary

A generally well-settled upper snowpack sits atop a complex snowpack with several layers of note.

A layer of buried surface hoar buried 50 to 70 cm deep has been an active avalanche problem. It is less of a concern in areas where a strong, supportive crust exists above the surface hoar layer.

The lower snowpack is typically characterized by sugary, facetted crystals and a crust. Avalanches have been stepping down to this layer.

Snowpack depths at treeline average 70-120 cm with significant variability across the region.

Weather Summary

Saturday night

Mostly cloudy with trace amounts of new snow, ridgetop wind <10 km/h south, treeline temperature -6 °C.

Sunday

Mostly cloudy with trace amounts of snow, ridgetop wind <10 km/h south, treeline temperature -4 °C.

Monday

A mix of sun and cloud, ridgetop wind <10 km/h southeast, treeline temperature -5 °C.

Tuesday

A mix of sun and cloud, ridgetop wind <10 km/h, treeline temperature -6 °C.

More details can be found in the Mountain Weather Forecast.

Terrain and Travel Advice

Uncertainty is best managed through conservative terrain choices at this time.
Avoid shallow snowpack areas, rock outcroppings and steep convex terrain where triggering is most likely.

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.

Deep Persistent Slabs

Deep Persistent Slab avalanches are the release of a thick cohesive layer of hard snow (a slab), when the bond breaks between the slab and an underlying persistent weak layer deep in the snowpack. The most common persistent weak layers involved in deep, persistent slabs are depth hoar or facets surrounding a deeply buried crust. Deep Persistent Slabs are typically hard to trigger, are very destructive and dangerous due to the large mass of snow involved, and can persist for months once developed. They are often triggered from areas where the snow is shallow and weak, and are particularly difficult to forecast for and manage.