Avalanche Forecast
Regions: Dogtooth, East Purcell, Purcells, St. Mary, West Purcell.
A complex snowpack with multiple weak layers is best managed by sticking to lower angle, low consequence terrain. Large persistent and deep persistent slab avalanches are reported every two or three days.
Confidence
Moderate
Avalanche Summary
No notable avalanches were reported on Sunday, but several notable large persistent and deep persistent slab avalanches have occurred in the Purcells over the past week. Here are some recent avalanches that illustrate the weak snowpack structure:
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 Kimberley 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
Open terrain has been heavily wind affected. 40 to 80 cm of snow since late January is settling above a layer of surface hoar, facets, and/or crust. This layer has become reactive in the southern and western parts of the Purcells, where it is more deeply buried.
The lower snowpack contains a widespread layer of large, weak facets that is typically 80 to 150 cm deep. Snowpack depths at treeline range between 80 and 200 cm, with the shallowest depths found on the eastern edge of the Purcells.
Weather Summary
Monday night
Partly cloudy, isolated flurries with 1 to 5 cm of snow, 20 km/h northwest wind, treeline temperatures drop to -10 ºC.
Tuesday
Mix of sun and cloud, no significant precipitation, 20 km/h northeast wind, treeline temperatures around -8 °C.
WednesdayMostly sunny, no precipitation, 30 km/h west wind, treeline temperatures around -8 °C.
ThursdayMostly sunny, no precipitation, 30 km/h southwest wind, treeline temperatures around -8 °C.
More details can be found in the Mountain Weather Forecast.
Terrain and Travel Advice
- 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 40 to 80 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
Wind slab avalanches are possible to trigger in lee terrain after recent snow has been redistributed by southwest wind. The bond of this snow to underlying layers is suspect.
Aspects: North, North East, East, South East, North West.
Elevations: Alpine, Treeline.
Likelihood: Possible
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