Avalanche Forecast
Regions: Sea To Sky.
The structurally weak snowpack will need some time to stabilize with all the load from recent snow and strong wind. The next storm will start to impact the region midday Monday.
Confidence
Moderate - Uncertainty is due to how quickly the snowpack will recover and gain strength.
Weather Forecast
SUNDAY NIGHT: Clearing but with isolated flurries, local accumulation 5 cm, moderate southwest wind, alpine temperature -10 C, freezing level below valley bottom.
MONDAY: Cloudy with snowfall, accumulation 10 to 15 cm, moderate southwest wind, alpine temperature -7 C, freezing level rising to 800 m.
TUESDAY: Cloudy with snowfall, accumulation 40 to 60 cm, strong southwest wind, alpine temperature -3 C, freezing level 1000 m.
WEDNESDAY: Morning snowfall and afternoon clearing, accumulation 10 to 15 cm, light northwest wind, alpine temperature -10 C, freezing level below valley bottom.
Avalanche Summary
Many avalanches released on the weak faceted grains described in the snowpack summary on Saturday. They were large avalanches (up to size 2.5) and triggered by explosives. They generally occurred at treeline and alpine elevations. Otherwise, many storm slab avalanches were also triggered by explosives, naturally, and by humans.
Snowpack Summary
Stormy conditions are forecast to continue in the region on Monday, with another 10 to 20 cm possible by the end of the day. This adds to the 50 to 80 cm that has already fallen in the past couple days. Southwest wind has redistributed much of the snow, loading lee terrain features in exposed terrain. All the storm snow may overly a touchy weak layer of feathery surface hoar, making storm slabs particularly touchy.
In parts of the region near the bottom of the snowpack around 150 to 200 cm deep, sugary faceted grains and a hard melt-freeze crust exist from mid-November. This is is an indicative snowpack setup for large and destructive avalanches. The likelihood of natural and human-triggered avalanches on this layer remains elevated with the loading occurring during this stormy period.
Terrain and Travel
- Travel in alpine terrain is not recommended.
- Avoid exposure to overhead avalanche terrain, avalanches may run surprisingly far.
- Storm slabs in motion may step down to deeper layers resulting in large avalanches.
Avalanche Problems
Storm Slabs
Many storm slab avalanches have occurred in the region with the wallop of snow that has accumulated in the past few days. The slabs are likely deepest and touchiest in lee terrain features at treeline and alpine elevations and in large openings below treeline. These slabs may take more time to stabilize as the region continues to receive more snowfall in the coming days.
Aspects: All aspects.
Elevations: All elevations.
Likelihood: Likely - Very Likely
Expected Size: 1.5 - 2.5
Persistent Slabs
A touchy weak layer is buried near the bottom of the snowpack. This layer has been responsible for many large, destructive avalanches in the region on a daily basis. The likelihood of triggering this layer remains elevated and the consequence of doing so would be severe.
Aspects: All aspects.
Elevations: Alpine, Treeline.
Likelihood: Possible - Likely
Expected Size: 2 - 3.5