Avalanche Forecast
Regions: North Rockies.
Recently formed slabs may remain triggerable by riders on Tuesday. New slabs will likely rapidly form during Wednesday's storm.
Confidence
Moderate - Uncertainty is due to the limited number of field observations. Uncertainty is due to the track & intensity of the incoming weather system.
Weather Forecast
MONDAY NIGHT: Mostly cloudy with isolated flurries, accumulation 1 to 3 cm, 30 km/h northwest wind, alpine temperature -9 C.
TUESDAY: Cloudy with snowfall, accumulation 5 to 10 cm, 30 km/h west wind, alpine temperature -8 C.
WEDNESDAY: Cloudy with snowfall, accumulation 20 to 40 cm, 50 km/h northwest wind, alpine temperature -5 C.
THURSDAY: Partly cloudy, 20 km/h northwest wind, alpine temperature -7 C.
Avalanche Summary
The recent snow was reported as being reactive to rider traffic over the weekend, particularly in steep wind-affected terrain. Looking forward, storm and wind slabs could continue to be triggered by riders as the wind speed remains elevated. New slabs are likely to develop on Wednesday.
Snowpack Summary
Around 20 to 30 cm of snow accumulated over the weekend for most riding areas. Southwest wind has likely formed wind slabs up high, as the snow is blown around at treeline and alpine elevations. The snow may also have settled into storm slabs, particularly in steep terrain sheltered from the wind. This snow overlies a hard melt-freeze crust up to treeline and to mountain tops on sun-exposed slopes. Another 20 to 40 cm of snow may accumulated by Wednesday afternoon, forming new storm and wind slabs. Cornices are very large along ridgelines and always have the possibility of failing naturally or from the weight of a human.
A weak layer of facets buried mid-February may be found around 100 to 120 cm deep, or shallower in the east of the region and in thin snowpack areas. The most likely place to trigger this layer is where the snowpack is shallow in alpine terrain. Large loads, such a cornice falls or multiple sleds on the same slope, often trigger slopes that single rider couldn't trigger.
Terrain and Travel
- Watch for changing conditions today, storm slabs may become increasingly reactive.
- Watch for newly formed and reactive wind slabs as you transition into wind affected terrain.
- Avoid exposure to slopes that have cornices overhead.
- Be aware of the potential for large avalanches due to the presence of a persistent slab.
- Avoid areas with a thin or variable snowpack.
Avalanche Problems
Storm Slabs
The weekend's snow may be settling into storm slabs that could be triggered by riders. New slabs are also likely to form on Wednesday during a strong storm. Assess for slab properties during your travels and use particular caution in steep, committing terrain with high consequences. Note that wind slabs are also likely find in exposed terrain from storm snow being blown into lee terrain features from strong southwest wind.
Aspects: All aspects.
Elevations: All elevations.
Likelihood: Possible - Likely
Expected Size: 1 - 2
Persistent Slabs
The persistent slab problem is most likely on the eastern slopes of the region (e.g., Kakwa, Tumbler Ridge) and in areas where the snowpack is thin. Steep, rocky slopes with a shallow or thin to thick snowpack in the alpine are the most likely places to trigger buried weak layers. This problem likely won't go away until substantial snowpack warming occurs.
Aspects: All aspects.
Elevations: Alpine.
Likelihood: Unlikely
Expected Size: 2 - 3