Avalanche Forecast

Archived

Nov 28th, 2021–Nov 29th, 2021

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 and human triggered avalanches likely.

Treeline

Natural and human triggered avalanches likely.

Below Treeline

Natural avalanches unlikely, human triggered possible.

Regions

Purcells.

The snow pack and avalanche hazard varies throughout the range. Read the complete forecast to get the details specific to your region.

Confidence

Low - Uncertainty is due to extremely variable snowpack conditions reported through the region.

Weather Forecast

Sunday night: the North half of the range will see freezing levels fall to 1000m with moderate West to Southwest winds. The South half of the range will see warmer temps and strong winds from the Southwest. Freezing levels will stay as high as 1600m. Up to 10mm throughout the range.

Monday: No precipitation during the day. The freezing level will be around 1600m throughout the range and winds will be moderate from the West.

Tuesday: Freezing levels will start around 1500m and rise to 2000m as another storm hits the range. 5 to 20mm of precipitation will fall in the evening with the largest amounts of precipitation in the Dogtooth range. winds will be strong from the Southwest.

Wednesday: The storm will reach its peak early in the morning. Freezing levels around 2000m and strong winds from the Southwest. Up to 15mm of precipitation with the largest amounts in the Dogtooth.

Avalanche Summary

On Sunday numerous natural avalanches up to size 2 were observed in the Toby creek drainage. These avalanches ran on a surface hoar layer believed to be widespread in this area above 1600m.

Several storm slab avalanches up to size 1.5 were observed in the North part of the range.

Snowpack Summary

Fresh wind slabs have been formed in the treeline and alpine. This hazard is greatest in the North half of the range. A surface hoar layer has been observed down 30 to 40cm in the Toby Creek drainage. A mid November rain crust is down 30 to 60cm and exists below 2100m.

Several early season crusts exist throughout the lower pack. A late October facet/crust layer sits at the bottom of the snowpack. it likely only exists above 1900m.

Average snowpack depth at treeline is 100 to 180cm with the deepest snow pack found around the Bugaboos.

Terrain and Travel

Watch for newly formed and reactive wind slabs as you transition into wind affected terrain.
Avoid thin areas like rock outcroppings where you're most likely to trigger avalanches failing on deep weak layers.

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.

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.