Avalanche Forecast

Archived

Jan 10th, 2023–Jan 11th, 2023

Alpine

Natural avalanches possible, human triggered probable.

Treeline

Natural avalanches possible, human triggered probable.

Below Treeline

Natural avalanches unlikely, human triggered possible.

Alpine

Natural avalanches possible, human triggered probable.

Treeline

Natural avalanches possible, human triggered probable.

Below Treeline

Natural avalanches unlikely, human triggered possible.

Alpine

Natural avalanches possible, human triggered probable.

Treeline

Natural avalanches possible, human triggered probable.

Below Treeline

Natural avalanches unlikely, human triggered possible.

Regions

Purcells, Dogtooth, East Purcell, West Purcell.

Continue to make conservative terrain choices and avoid shallow rocky slopes.

In General the snowpack is weak and there is an ongoing risk of triggering a deep persistent slab.

Confidence

Moderate

Avalanche Summary

On Monday evening we received reports of a fatal avalanche accident. This Avalanche occurred on a west facing slope at treeline in the southern Selkirk mountains. This avalanche did not occurre in this forecast region but similar snowpack conditions exist in the Purcells. This MIN report has more details.

Please continue to share any observations or photos on the Mountain Information Network.

Snowpack Summary

Wind effected surfaces exist on exposed treeline and alpine features. A new surface hoar layer can be found just below the surface as well as a crust on some steep south facing slopes.

The upper snowpack continues to settle and bond with mild temperatures. The mid and lower snowpack is generally weak and faceted, with a number of weak layers. Of significant concern is a layer down 30 to 50 cm from the surface consisting of a crust, facets, and/or surface hoar. And a layer of large facets and a crust down roughly 50 to 110 cm from the surface. The snow below this deeper weak layer is unconsolidated and weak.

Snowpack depths remain highly variable, ranging from 60 to 150 cm at treeline.

Weather Summary

Tuesday Night

Cloudy with trace amounts of new snow expected. Light southwest winds and a low of -12 at 1800m.

Wednesday

Cloudy with some sunny breaks and the possibility light flurries bringing trace amounts of new snow. Light southerly winds and a high of -6 at 1800m.

Thursday

Cloudy with up to 5cm of new snow expected. Strong southerly winds and freezing levels rising to 1500m.

Friday

Stormy with up to 10cm of new snow expected at treeline and above. Rain at lower elevations. Freezing levels around 1900m . Moderate to strong southerly winds.

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 steep, rocky, and wind effected areas where triggering slabs is more likely.
Be mindful that deep instabilities are still present and have produced recent large avalanches.

Problems

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.

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.