Avalanche Forecast
Regions: Sea To Sky.
Intense stormy conditions are expected for Tuesday. Natural and human-triggered avalanches will be very likely to occur and they could reach the valley bottom. Travel in avalanche terrain is not recommended.
Confidence
No Rating - We are confident the likelihood of avalanche will increase with the arrival of the forecast weather.
Weather Forecast
MONDAY NIGHT: Cloudy with snowfall, accumulation 10 to 30 cm, moderate southwest wind, alpine temperature -3 C, freezing level rising to 1300 m.
TUESDAY: Cloudy with snowfall, accumulation 30 to 50 cm, strong southwest wind, alpine temperature -2 C, freezing level 1500 m.
WEDNESDAY: Morning snowfall and afternoon clearing, accumulation 10 cm, light northwest wind, alpine temperature -11 C, freezing level below valley bottom.
THURSDAY: Clear skies, light northwest wind, alpine temperature -11 C, freezing level below valley bottom.
Avalanche Summary
Many avalanches released on the weak faceted grains described in the snowpack summary on the weekend. They were large avalanches (up to size 2.5) and triggered by explosives. They generally occurred at treeline and alpine elevations. Many storm slab avalanches were also triggered by explosives, naturally, and by humans.
Avalanche activity is expected to increase through the night and on Tuesday as the storm snow accumulates. Storm slab avalanches will be very likely to be triggered and they may step down to deeper weak layers in parts of the region, forming very large avalanches.
Snowpack Summary
40 to 80 cm of snow is forecast to accumulate Monday night into Tuesday, falling with strong southwest wind and with a rise of the freezing level to around 1500 m. Storm slabs will quickly develop and be especially touchy in lee terrain features. Below the rain-snow line, loose wet avalanches are likely to prevail. The snow may be loading touchy weak layer of feathery surface hoar buried around 100 to 150 cm.
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
- Avoid all avalanche terrain during periods of heavy loading from new snow, wind, or rain.
- If triggered, storm slabs in-motion may step down to deeper layers and result in very large avalanches.
- Avoid traveling in runout zones. Avalanches have the potential to run to the valley floor.
Avalanche Problems
Storm Slabs
40 to 80 cm of snow is forecast to accumulate in the region, which will form new storm slabs. The snow will be accompanied by an increase in the freezing level to around 1500 m and strong southwesterly wind, making slabs particularly touchy. There is potential for storm slabs to step down to deeper weak layers, forming very large and destructive avalanches.
Aspects: All aspects.
Elevations: All elevations.
Likelihood: Very Likely
Expected Size: 1 - 2.5
Persistent Slabs
A touchy weak layer is buried near the bottom of the snowpack in parts of the region. This layer has been responsible for many large, destructive avalanches on a daily basis. The likelihood of triggering this layer will increase as the storm loads it.
Aspects: All aspects.
Elevations: Alpine, Treeline.
Likelihood: Likely
Expected Size: 2 - 3.5