Avalanche Forecast

Archived

Nov 26th, 2021–Nov 27th, 2021

Alpine

Natural avalanches possible, human triggered probable.

Treeline

Natural avalanches unlikely, human triggered possible.

Below Treeline

Natural avalanches unlikely.

Alpine

Natural and human triggered avalanches likely.

Treeline

Natural and human triggered avalanches likely.

Below Treeline

Natural avalanches unlikely, human triggered possible.

Alpine

Natural avalanches possible, human triggered probable.

Treeline

Natural avalanches unlikely, human triggered possible.

Below Treeline

Natural avalanches unlikely.

Regions

Purcells.

Pay attention to how the wind has redistributed recent snow as you gain elevation. Snow fall varies throughout the region.

Confidence

Moderate - Uncertainty is due to the speed, direction, or duration of the wind and its effect on the snowpack.

Weather Forecast

Friday night: A break in the storms will arrive over the Purcells. Freezing levels will fall to valley bottom. Winds will be moderate from the West.

Saturday: Cold and Dry conditions across the Purcells in the morning. A split in the weather will happen in the evening with the North half of the range seeing less snow, freezing levels at valley bottom and light to moderate Southwest winds. Meanwhile the Southern half will see freezing levels rise to 1500m with moderate to strong winds in the alpine. 10 to 20cm of new snow.

Sunday: The storm will be most intense South of the Bugaboos where the freezing level will hit 2000m and 30cm of new snow will fall with strong South west winds. The Dogtooth will see up to 20cm with moderate to strong Southwest winds and freezing levels rising to 1500m.

Monday: weather will clear throughout the day and winds will move to light to Moderate from the West. Freezing levels in the North will fall to valley bottom, Freezing levels will fall to 1500m in the South.

Avalanche Summary

Several size 1 natural avalanches were observed in the Dogtooth range.

Snowpack Summary

New wind slabs have formed in exposed treeline and alpine features. 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.

snowpack height at treeline is around 50 to 140cm.

Terrain and Travel

Be alert to conditions that change with elevation and wind exposure.
Avoid areas where the snow feels stiff and/or slabby.
Be careful with wind loaded pockets, especially near ridge crests and roll-overs.
Use caution on large alpine slopes, especially around thin areas that may propagate to deeper instabilities.

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.