Avalanche Forecast
Regions: Kootenay Boundary.
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
High - We are confident the likelihood of avalanche will increase with the arrival of the forecast weather.
Weather Forecast
MONDAY NIGHT: Cloudy with snowfall, accumulation 15 to 30 cm, light to moderate west wind, alpine temperature -5 C, freezing level 1000 m.
TUESDAY: Cloudy with snowfall, accumulation 25 to 35 cm, moderate to strong southwest wind, alpine temperature -3 C, freezing level 1400 m.
WEDNESDAY: Morning snowfall and afternoon clearing, accumulation 20 to 30 cm, light northwest wind, alpine temperature -6 C, freezing level 1000 m.
THURSDAY: Mix of sun and cloud, light northwest wind, alpine temperature -12 C, freezing level below valley bottom.
Avalanche Summary
Many storm slab avalanches were triggered by skiers and explosives on Monday. The avalanches were generally large (size 1.5 to 2.5).
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, forming very large avalanches.
Snowpack Summary
40 to 60 cm of snow is forecast to accumulate Monday night into Tuesday, falling with strong west wind. 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.
This snow is loading multiple buried weak layers of feathery surface hoar found 50 to 150 cm in the snowpack. The base of the snowpack is also weak in parts of the region, where it consists of sugary faceted snow around a melt-freeze crust.
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
- 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 60 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 1400 m and strong westerly wind, making slabs particularly touchy. There is potential for storm slabs to step down to deeper weak layers, forming large and destructive avalanches.
Aspects: All aspects.
Elevations: All elevations.
Likelihood: Very Likely
Expected Size: 1 - 2.5
Persistent Slabs
Several persistent weak layers are buried in the snowpack in the region. They will be loaded with the stormy conditions, adding stress to them that could reach their tipping point.
Aspects: All aspects.
Elevations: All elevations.
Likelihood: Likely
Expected Size: 2 - 3.5