Avalanche Forecast

Archived

Dec 29th, 2023–Dec 30th, 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 possible, human triggered probable.

Treeline

Natural avalanches unlikely, human triggered possible.

Below Treeline

Natural avalanches unlikely.

Regions

Purcells, Dogtooth, East Purcell, West Purcell.

Above-zero temperatures in the high alpine today adds to an already complex snowpack situation, with potential to further destabilize buried weak layers. Stick to conservative terrain.

Confidence

Moderate

Avalanche Summary

Most recent avalanche activity has been from explosive control work in the alpine;

persistent layers stepping down to the ground, running up to size 2 in the Dogtooth range
small wind slabs in the northwest Purcells
ski cuts produced size 1 loose dry 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 is down roughly 50 to 70 cm and remains concerning in much of the region. 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.

Snowpack depths at treeline average roughly 70-120 cm. However, there is significant variability in both snowpack structure and depths across the region.

Weather Summary

Friday night

Partly cloudy. Light southeast wind. Treeline temperature -8 °C. Freezing level valley bottom with an above freezing layer developing 2300-2700 m.

Saturday

A mix of sun and cloud. Light southwest wind. Treeline temperature -4 °C. Freezing level 900 m with an above freezing layer 2300-2700 m.

Sunday

Mostly cloudy with trace amounts of snow. Light northwest wind. Treeline temperature -4 °C. Freezing level 1000 m.

Monday

Mostly cloudy. Light southerly wind. Treeline temperature -6 °C. Freezing level 700 m.

More details can be found in the Mountain Weather Forecast.

Terrain and Travel Advice

Extra caution for areas experiencing rapidly warming temperatures for the first time.
In times of uncertainty conservative terrain choices are our best defense.
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.