Avalanche Forecast
Issued: Dec 22nd, 2019 4:00PM
The alpine rating is , the treeline rating is , and the below treeline rating is Known problems include Persistent Slabs and Storm Slabs.
mconlan,
Avalanche Canada
Clear skies may lure you into bigger terrain, but this is not the time to expose yourself. The recent snow is resting on a weak layer ready to fail with the weight of a human. Read more here. Best to avoid alpine avalanche terrain and travel conservatively at treeline.
Summary
Confidence
Weather Forecast
SUNDAY NIGHT: Clear skies, light northwest wind, alpine temperature -6 C, freezing level below valley bottom.
MONDAY: Clear skies, light southwest wind, alpine temperature -7 C, freezing level below valley bottom.
TUESDAY: Cloudy with light snowfall, accumulation 1 to 3 cm, moderate south wind, alpine temperature -8 C, freezing level below valley bottom.
WEDNESDAY: Cloudy with light snowfall, accumulation 1 to 3 cm, light northeast wind, alpine temperature -7 C, freezing level below valley bottom.
Avalanche Summary
Many large persistent slab avalanches were triggered by explosives on Saturday and Sunday. The avalanches failed on the mid-November weak layer described in the Snowpack Summary. Some of the avalanches were remotely triggered, meaning the weak layer was triggered from one spot and propagated through the snowpack to reach the steeper terrain where the avalanche released.
Human-triggered avalanches are expected to be very likely to occur on Monday at higher elevations. We recommend avoidance of alpine avalanche terrain and very conservative decision-making at treeline, given this weak snowpack.
Snowpack Summary
Around 70 to 120 cm of recent snow fell with very strong southwest wind. All of this snow overlies a weak layer of surface hoar as well as sugary faceted grains and hard melt-freeze crust buried mid-November, which is a recipe for large and destructive avalanches. These weak layers may be found anywhere from about 80 to 150 cm deep.
This weak and touchy snowpack is highly atypical for the region and may persist for some time. Conservative terrain travel along with periods of avoidance of avalanche terrain will be imperative to manage your risk until the weak snow gains strength.
Terrain and Travel
- Travel in alpine terrain is not recommended.
- Don't let the desire for deep powder pull you into high consequence terrain.
- Persistent slabs have potential to pull back to lower angle terrain.
- Make conservative terrain choices and avoid overhead hazard.
Problems
Persistent Slabs
A touchy weak layer is buried in the lower half of the snowpack. This layer has been responsible for many large avalanches in the region over the past two weeks. The consequence of triggering this layer would be severe. This snowpack setup is atypical for the region, which will require diligent terrain travel, conservative decision-making, and periods of avoidance until the weak layer strengthens. At the moment, expert-level terrain selection is needed, as there are many areas where you could trigger large, destructive avalanches.
Aspects: All aspects.
Elevations: Alpine, Treeline.
Likelihood
Expected Size
Storm Slabs
Storm slabs formed during the latest storm may remain touchy to human traffic. Storm slab avalanches may step down to a buried weak layer, forming destructive avalanches that could travel far.
Aspects: All aspects.
Elevations: Alpine, Treeline.
Likelihood
Expected Size
Valid until: Dec 23rd, 2019 5:00PM
