Avalanche Forecast
Issued: Jan 4th, 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
The snowpack likely needs more time to stabilize, especially where recent snow overlies weak layers. There is also still concern for triggering deeper weak layers. Conservative decision-making is essential to manage these avalanche problems.
Summary
Confidence
Moderate - Uncertainty is due to how quickly the snowpack will recover and gain strength.
Weather Forecast
SATURDAY NIGHT: Partly cloudy, moderate west wind, alpine temperature -9 C, freezing level 500 m.
SUNDAY: Mostly cloudy with afternoon snowfall, accumulation 2 to 5 cm, moderate southwest wind, alpine temperature -7 C, freezing level 800 m.
MONDAY: Mix of sun and cloud with afternoon snowfall, accumulation 2 to 5 cm, moderate west wind, alpine temperature -9 C, freezing level 500 m.
TUESDAY: Cloudy with snowfall, accumulation 15 to 25 cm, moderate to strong southwest wind, alpine temperature -3 C, freezing level 1100 m.
Avalanche Summary
Small avalanches were observed in the most recent storm snow on Friday.
On Thursday, many large storm slab avalanches were reported, being triggered naturally and by humans. They were generally 20 to 50 cm deep and occurred at treeline and alpine elevations. Further, two large avalanches occurred on the deeply buried weak layers described in the snowpack summary, suggesting that they are still problematic layers.
Snowpack Summary
Around 40 to 60 cm of recent storm snow has formed touchy storm slabs. The snow has been redistributed by strong southwest wind, making the slabs thicker and more reactive in lee features near ridges. These slabs have been capped with a thin layer of ice at all elevations in many parts of the region, which may limit further wind transportation. The storm snow may overly 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, as it is capable of producing large and destructive avalanches. 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 relatively thin.
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 formed the past few days may continue to be reactive to human activity, particularly where they overly weak surface hoar. Thicker and potentially touchier slabs may be found in wind-loaded terrain features, such as near ridges.
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 5th, 2020 5:00PM
