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Avalanche Forecast

Archived

Dec 31st, 2021–Jan 1st, 2022

Alpine
Natural avalanches possible, human triggered probable.
Treeline
Natural avalanches unlikely, human triggered possible.
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 unlikely, human triggered possible.
Below Treeline
Natural avalanches unlikely, human triggered possible.

Regions

Banff Yoho Kootenay.

Winds, warming, and a bit of snow expected to arrive this weekend will be a significant change that could really shake up the snowpack. Make conservative terrain selections and consider your exposure to overhead terrain. Natural activity is expected.

Weather Forecast

A low pressure system will cross the divide Saturday. As temperatures rise 10 to 15 degrees C, expect alpine winds to reach extreme values by the afternoon as light snowfall starts on the divide. Snow continues at a moderate rate for Sunday as the winds diminish to strong midday and temperatures rise a further 10 degrees C. 

Snowpack Summary

10-40 cm of snow last week and recent wind from various directions has developed wind slabs in the alpine. There is 50-70 cm over the Dec. 2 crust/facet combo which exists below 2200m and appears to be waking up as a persistent weak layer. Shallow areas (<100 cm) have weaker basal facets which also present cause for concern as temperatures rise.

Avalanche Summary

There was a skier triggered size 2 avalanche at 2000m in Kootenay NP Thursday. This appears to have been on the Dec. 2nd crust/facets. It also appears that another party triggered a smaller slab in the same area today. The ski hills worked with recent windslabs in the alpine yesterday however nothing new was reported today.

Confidence

Intensity of incoming weather systems is uncertain on Saturday

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.

Loose Dry

Loose Dry avalanches are the release of dry unconsolidated snow and typically occur within layers of soft snow near the surface of the snowpack. These avalanches start at a point and entrain snow as they move downhill, forming a fan-shaped avalanche. Other names for loose-dry avalanches include point-release avalanches or sluffs.