Avalanche Forecast
Regions: Dogtooth, East Purcell, Purcells, St. Mary, West Purcell.
The message remains the same – a complex, and generally weak snowpack is best managed by sticking to lower angled, low consequence terrain. Large persistent slab or deep persistent slab avalanches are reported every two or three days.
Confidence
Moderate
Avalanche Summary
Over the past week there have been continual reports of large persistent and deep persistent slab avalanches across the Purcells. Here are some recent examples that illustrate the currently dangerous snowpack conditions:
On Saturday, skiers at Quartz Creek remotely-triggered a size 3 avalanche on a northwest-facing alpine slope at 2300 m. It failed on a 40 to 80 cm deep weak layer.
On Friday, skiers near Invermere remotely-triggered a size 2 on a north aspect at 2400 m. The avalanche started on a 30 cm deep surface hoar layer and stepped down to the deep persistent weak layer.
On Thursday, skiers near Kimberlely reported several very large persistent slab avalanches, including a size 3 avalanche that was remotely-triggered on a treeline feature.
Smaller size 1 to 2 wind slab avalanches have also been reported in alpine terrain over the past few days.
Snowpack Summary
30 to 60 cm of snow since late January is settling and being redistributed by southwest wind. A weak layer of surface hoar or facets and crust is buried beneath that snow, and has become reactive in the southern and western parts of the Purcells where it is more deeply buried (e.g., along Kootenay Lake and the St. Mary drainage). A layer from late November is found 75 to 150 cm deep throughout the Purcells and is part of a generally weak, faceted lower snowpack. Snowpack depths range between 90 and 200 cm at treeline, with the shallowest depths found on the eastern edge of the Purcells.
Weather Summary
Sunday night
Cold front crossing the Purcells overnight, 5 to 15 cm of snow, 50 to 80 km/h southwest wind, treeline temperatures around -6 ºC.
Monday
Mostly cloudy with convective flurries bringing up to 5 cm of snow, 40 km/h southwest wind, treeline temperatures around -4 °C.
TuesdaySunny with a few clouds, no significant precipitation, 20 km/h north wind, treeline temperatures drop to -10 °C.
WednesdayMix of sun and cloud, no precipitation, 30 km/h northwest wind, treeline temperatures around -8 °C.
More details can be found in the Mountain Weather Forecast.
Terrain and Travel Advice
- It's critical to stay disciplined and choose only well supported, low consequence lines.
- Use careful route-finding and stick to moderate slope angles with low consequences.
- Avoid rock outcroppings, convexities, and anywhere the snowpack is thin and/or variable.
- Avoid steep convex slopes.
- Be especially cautious as you transition into wind affected terrain.
Avalanche Problems
Persistent Slabs
Large avalanches have been triggered on a 30 to 60 cm deep layer of surface hoar and facets that was buried in late January. This problem seems most concerning in the western and southern Purcells where the layer is more deeply buried and primed for human triggering. Steep open slopes should be avoided.
Aspects: All aspects.
Elevations: All elevations.
Likelihood: Possible - Likely
Expected Size: 2 - 2.5
Wind Slabs
New snow combined with wind will form fresh wind slabs in lee terrain features.
Aspects: North, North East, East, South East, North West.
Elevations: Alpine, Treeline.
Likelihood: Possible - Likely
Expected Size: 1 - 2
Deep Persistent Slabs
It remains possible for riders to trigger a weak layer of facets near the base of the snowpack. The most likely area to trigger it is in shallow areas with variable snow depths. Avoid thin and rocky start zones and select routes that avoid travelling through or under large avalanche paths.
Aspects: All aspects.
Elevations: Alpine, Treeline.
Likelihood: Unlikely - Possible
Expected Size: 2.5 - 4