Avalanche Forecast
Issued: Jan 3rd, 2020 4:00PM
The alpine rating is , the treeline rating is , and the below treeline rating is Known problems include Storm Slabs and Persistent Slabs.
mconlan,
Avalanche Canada
Storm slab avalanches continue to be triggered in the region. There is also still concern for triggering buried weak layers. Conservative decision-making is essential to manage these avalanche problems.
Summary
Confidence
Weather Forecast
FRIDAY NIGHT: Increasing cloud with early-morning flurries, accumulation 2 to 5 cm, moderate to strong southwest wind, alpine temperature -2 C, freezing level 1400 m.
SATURDAY: Mix of sun and cloud with isolated flurries, accumulation 5 to 10 cm, moderate to strong west wind, alpine temperature -9 C, freezing level 1000 m.
SUNDAY: Cloudy with light snowfall, accumulation 2 to 5 cm, moderate southwest wind, alpine temperature -7 C, freezing level 800 m.
MONDAY: Cloudy with light snowfall, accumulation 2 to 5 cm, moderate southwest wind, alpine temperature -8 C, freezing level 700 m.
Avalanche Summary
Many avalanches were reported on Thursday of large storm slab avalanches, being triggered naturally and by humans. They have generally been 20 to 50 cm deep and occurring at treeline and alpine elevations. Two large avalanches occurred on the deeply buried weak layers described in the snowpack summary, indicating that they can still be triggered.
Snowpack Summary
Around 40 to 60 cm of recent storm snow has bonded to form a touchy storm slab problem. The snow has been redistributed by strong southwest wind, loading lee features near ridges. The storm snow overlies a weak layer of feathery surface hoar and a hard melt-freeze crust on sun-exposed aspects, which has increased the reactivity of these slabs.
There are multiple weak layers buried around 80 to 120 cm deep, including two more surface hoar layers and weak faceted snow near the bottom of of the snowpack. This fundamentally unstable snowpack structure remains a concern. It is possible that storm slab avalanches could step down to these deeper layers or the layers could be triggered in areas where the snowpack is thin, forming large and destructive avalanches.
Terrain and Travel
- Make conservative terrain choices and avoid overhead hazard.
- Watch for newly formed and reactive wind slabs as you transition into wind affected terrain.
- Be aware of the potential for large avalanches due to the presence of buried surface hoar.
- Storm slabs in motion may step down to deeper layers resulting in large avalanches.
Problems
Storm Slabs
Storm slabs continue to be reactive to human and natural activity, forming large avalanches. Thicker slabs are found in wind-loaded terrain features, particularly near ridges. Conservative terrain travel is required to avoid this avalanche problem.
Aspects: All aspects.
Elevations: All elevations.
Likelihood
Expected Size
Persistent Slabs
Several persistent weak layers are buried in the middle and lower half of the snowpack. Although these layers become harder to trigger as they get deeper, the destructive potential of a triggered avalanche increases. These layers could be triggered by humans where the snowpack is relatively thin or a storm slab avalanche could step down to them.
Aspects: All aspects.
Elevations: All elevations.
Likelihood
Expected Size
Valid until: Jan 4th, 2020 5:00PM
