Avalanche Forecast

Archived

Nov 27th, 2022–Nov 28th, 2022

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.

Alpine

Natural avalanches unlikely, human triggered possible.

Treeline

Natural avalanches unlikely, human triggered possible.

Below Treeline

Natural avalanches unlikely.

Regions

North Rockies, Sugarbowl, Kakwa, McGregor, Pine Pass, Tumbler.

Watch for wind slabs up high. Assess the bond of all the recent snow to the underlying snowpack, as we're getting to a critical depth where riders could trigger slabs that may propagate far.

Confidence

Moderate

Avalanche Summary

There have been no recent avalanche observations.

Looking forward, a cooling trend may decrease the likelihood of natural avalanches but riders could trigger wind slabs or the weak layers described in the Snowpack Summary.

Please consider sharing your observations via the Mountain Information Network to help us and fellow recreationists.

Snowpack Summary

Around 40 to 80 cm of snow accumulated over the past week at higher elevations with strong wind originating from the southwest but recently switching to the northeast. The wind has kept severely wind-exposed terrain bare and it has formed wind slabs in lee terrain features.

The storm snow overlies persistent weak layers formed mid-November of sugary faceted grains and surface hoar in sheltered terrain as well as a hard crust on steep sun-exposed slopes. Treeline and lower alpine are the most suspect elevations.

Average snowfall depths are around 20 to 60 cm below treeline and 100 to 120 cm in the alpine.

Weather Summary

Sunday Night

Partly cloudy with isolated flurries, accumulation 1 to 3 cm, 40 km northeast wind, treeline temperature -16 C.

Monday

Partly cloudy with isolated flurries, accumulation 1 to 3 cm, 20 to 40 km/h northeast wind, treeline temperature -18 C.

Tuesday

Partly cloudy with no precipitation, 20 km/h southeast wind, treeline temperature -22 C.

Wednesday

Mostly cloudy with snowfall, accumulation 1 to 3 cm, 40 km/h northeast wind, treeline temperature -21 C.

More details can be found in the Mountain Weather Forecast.

Terrain and Travel Advice

Recent wind has varied in direction so watch for wind slabs on all aspects.
Potential for wide propagation exists, fresh slabs may rest on surface hoar, facets and/or crust.
Make observations and assess conditions continually as you travel.

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.

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.