Avalanche Forecast
Regions: Boundary, East Stikine, Howson, Kitimat, Nass, Ningunsaw, Northwest Coastal, Rupert, Seven Sisters, Shames, Stewart, West Stikine.
A problematic weak layer has surprised riders and triggered large avalanches. Conservative terrain selection is your best defence against buried weak layers.
Confidence
Moderate
Avalanche Summary
On Friday, explosives triggered several small size 1-1.5 wind slab avalanches, with crowns 20-40 cm deep.
Thursday and Friday, natural and rider-triggered wind slab avalanches to size 2 were reported.
A persistent weak layer has recently produced very large natural and human-triggered avalanches, including remote-triggering up to 1 km away. On the 28th this near miss surprised riders, and this MIN describes avalanches triggered from valley bottom.
Snowpack Summary
5 to 15 cm of fresh snow covered older wind affected snow. Easterly winds have reverse loaded-features, and wind slabs can be found on various aspects. Soft snow still exists in sheltered terrain and in the trees.
Our primary concern is a persistent weak layer of surface hoar and facets overlying a crust. It is buried 50 to 100 cm deep in the southern parts of the region and up to 200 cm deep in areas north of Stewart. Several recent large avalanches have failed on this layer producing wide propagation.
The lower snowpack is well settled, with no deeper layers of concern. Treeline snow depths are around 160 cm.
Weather Summary
Saturday night
Cloudy with isolated flurries, trace to 10 cm of snow. 20 to 30 km/h south ridgetop wind. Treeline temperature -14 °C.
Sunday
Mostly cloudy. 25 to 40 km/h west ridgetop wind. Treeline temperature -6 °C.
Monday
Sunny. 30 to 70 km/h southwest ridgetop wind. Treeline temperature -4 °C.
Tuesday
Cloudy with flurries, up to 10 cm. 40 to 80 km/h southwest ridgetop wind. Treeline temperature -2 °C.
More details can be found in the Mountain Weather Forecast.
Terrain and Travel Advice
- Be aware of the potential for large avalanches due to buried weak layers.
- If triggered, wind slabs avalanches may step down to deeper layers resulting in larger avalanches.
- In times of uncertainty, conservative terrain choices are our best defense.
Avalanche Problems
Persistent Slabs
Recent large avalanches have failed on weak grains over a buried crust. This weak layer has shown wide propagation across large terrain features.
Aspects: All aspects.
Elevations: All elevations.
Likelihood: Possible
Expected Size: 1.5 - 2.5
Wind Slabs
Recent winds have varied in direction. Watch for wind slabs on all aspects and use caution as you enter wind-affected terrain.
Aspects: All aspects.
Elevations: Alpine, Treeline.
Likelihood: Possible
Expected Size: 1 - 1.5