Avalanche Forecast

Issued: Dec 8th, 2020 4:00PM

The alpine rating is considerable, the treeline rating is considerable, and the below treeline rating is moderate. Known problems include Storm Slabs.

Avalanche Canada swerner, Avalanche Canada

Email

Snowfall amounts are uncertain and it looks like the Northern part of the region will receive more than the South. If you see less than 25 cm of new snow in your riding area consider the avalanche danger to be MODERATE at treeline.

Summary

Confidence

Low - Forecast snowfall amounts are uncertain. Uncertainty is due to limitations in the field data.

Weather Forecast

The North end of the region (Elk Valley/ Crowsnest North) may see slightly higher snowfall amounts than in the South.

Wednesday: Mostly cloudy with light snow 5-20 cm. Alpine temperatures near -1.0 and ridgetop wind 20-50 km/hr. from the southwest. Freezing levels near 1700 m.

Thursday: A mix of sun and cloud. Alpine temperatures near -10 and freezing levels at the valley bottom. Ridgetop winds will be light from the southwest.

Friday: Mainly cloudy with light flurries. Alpine temperatures near -11 with the freezing level in the valley bottom. Ridgetop winds moderate to strong from the southwest.

Avalanche Summary

With the new snow and wind forecast overnight Tuesday and into Wednesday we may see some fresh avalanche activity either in the form of loose dry or storm and wind slabs. 

Have you been out? If so, we would love to hear about it on the Mountain Information Network. A picture is worth a thousand words! Thanks for your submissions. 

Snowpack Summary

Up to 20 cm of forecast new snow will likely bury the recent surface hoar (feather-like frost crystals) that exists on most aspects and elevations in wind-sheltered areas. The strong southwest winds likely destroyed some of the surface hoar on wind-exposed slopes, but in wind-sheltered areas the surface hoar may be alive and well. The new snow will likely show a poor bond to the old plethora of snow surfaces like surface hoar and crusts on solar aspects from last week’s sun and warm temperatures.

Isolated pockets of stiff and reactive wind slab may exist on leeward slopes during and after this wind event. These wind slabs may sit above a widespread rain crust from early November, which can be found up to 2500m and buried down 30-100cm. Weak snow may be developing around this crust.

However, given the stagnant weather pattern and a decreasing trend in instability, this problematic snowpack structure is not currently listed as a problem. We may expect to see it transition to our problems page once it becomes buried with new snow. It will be a layer to monitor as the season progresses.

The snowpack is generally thin, wind hammered, variable in wind-scoured areas and tapers rapidly at lower elevations. Snowpack depths at sheltered upper treeline elevations are nearing 100 cm and beginning to exceed the threshold for avalanches

Terrain and Travel

  • Watch for newly formed and reactive wind slabs as you transition into wind affected terrain.
  • Closely monitor how the new snow is bonding to the crust.
  • Recent new snow may be hiding windslabs that were easily visible before the snow fell.

Problems

Storm Slabs

An icon showing Storm Slabs

The new snow may show a poor bond to the variety of old snow surfaces its landing on. This may result in a reactive storm slab or small loose dry avalanches from steep terrain. Strong southwest winds may have formed deeper deposits on lee aspects building new and reactive wind slabs in the alpine and in "alpine-like" features near treeline, particularly where these slabs sit on top of a crust/facet layer from early November.

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Possible - Likely

Expected Size

1 - 2

Valid until: Dec 9th, 2020 4:00PM