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Avalanche Forecast

Archived

Dec 7th, 2022–Dec 8th, 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

Banff Yoho Kootenay, Little Yoho, Banff, East Side 93N, Kootenay, Lake Louise, LLSA, Sunshine, West Side 93N, Field.

The basal facets aren't getting any smaller, and we have a more traditional snowpack than we have had in the past couple of winters. There are some fresh wind slabs, as well as weak facets near the ground. Treat any slope that has a wind slab overlying facets or crusts with caution as the potential for human triggering is higher.

Confidence

Low

Avalanche Summary

One size 1.5 to 2 today in the Healy Creek area, failing on facets today. Lots of whumpfing in the Sunshine area overall, mainly on the facets. No other observations.

Snowpack Summary

5-25cm of snow and wind over the last few days has formed fresh wind slabs at higher elevations.

Here is an image of the typical snowpack in the Rockies; 81 cm snowpack at treeline at Crowfoot Glades. A few cm of low-density new snow on the surface, then about a 20-30 cm slab overlying the Nov 22 interface, below which facets and weak snow grains exist to ground. This snowpack is generally weak and will not handle much extra load.

Weather Summary

SW winds of 40-60 kph are expected overnight into Friday. Expected temperatures are -15C at ridgetop. On Friday, 20-40 kph winds are expected (some models showing higher values) with flurries and ridgetop temperatures ranging from -10C to -15C.

Problems

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.

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.

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.