Avalanche Forecast
Regions: Nass, Northwest Coastal, Rupert, Shames, Stewart, West Stikine.
Triggering large persistent slab avalanches on weak facets in the alpine is currently the primary concern.
Choose well-supported, low-consequence lines and watch for signs of instability.
Confidence
Low
Avalanche Summary
No avalanches were reported on Wednesday. However, observations in this region are currently very limited.
Two persistent slab avalanches were reported northwest of Terrace last Wednesday (April 12th). A skier triggered size 2 on a north aspect in the alpine and a size 2.5 on an east aspect in the alpine that was triggered by solar radiation. Both failed on a layer of weak facets and/or surface hoar down 40-50 cm.
A fatal avalanche occurred north of Stewart last Tuesday (11th). It was a skier-triggered size 3 persistent slab avalanche that occurred on a northeast aspect in the alpine.
Observations are limited at this time of year, please consider sharing any information or photos you have on the Mountain Information Network to help guide our forecasts.
Snowpack Summary
10-20 cm of recent snow and strong southeast wind formed wind slabs that may remain reactive to human triggers in isolated locations in the alpine. A crust exists up to ridgetop on south-facing slopes and on all aspects up to approximately 1300 m.
The primary concern is two buried weak layers down 40-140 cm deep in most areas. They include facets and surface hoar in shaded areas and a melt-freeze crust elsewhere. Numerous human-triggered persistent slab avalanches have occurred on these layers during the past week.
The mid and lower snowpack is considered generally strong and well-bonded. In the far northern reaches of the region, basal facets may exist which are currently considered inactive. This layer may become active with abrupt changes to the snowpack, such as rapid loading (heavy snowfall or rain) or prolonged warming.
Weather Summary
Thursday Night
Partly cloudy with isolated flurries; 0-10 cm / 20 km/h east ridgetop wind / Temperature at treeline around -3 C / Freezing level 1000 m
Friday
Mix of sun and cloud with isolated flurries; 0-5 cm / 10 km/h south ridgetop wind / Temperature at treeline around -1 C / Freezing level 1400 m
Saturday
Snow; 10-15 cm / 50 km/h south ridgetop wind / Temperature at treeline around -3 C / Freezing level 1200 m
Sunday
Mix of sun and cloud with isolated flurries; 0-5 cm / 20 km/h south ridgetop wind / Temperature at treeline around -2 C / Freezing level 1300 m
More details can be found in the Mountain Weather Forecast.
Terrain and Travel Advice
- Potential for wide propagation exists, fresh slabs may rest on surface hoar, facets and/or crust.
- Watch for signs of instability like whumpfing, hollow sounds, shooting cracks or recent avalanches.
- Use conservative route selection. Choose simple, low-angle, well-supported terrain with no overhead hazard.
- If triggered, wind slabs avalanches may step down to deeper layers resulting in larger avalanches.
- Wind slabs may be poorly bonded to the underlying crust.
Avalanche Problems
Persistent Slabs
Numerous large persistent slab avalanches were triggered by riders in the alpine a little over a week ago. (Apr. 10-12)
The primary concern is a layer of facets and surface hoar buried anywhere from 40-140 cm on shaded slopes. On other slopes, this layer is a crust with facets above. Avoid steep open slopes capable of producing large avalanches.
Aspects: All aspects.
Elevations: Alpine.
Likelihood: Possible - Likely
Expected Size: 1.5 - 3
Wind Slabs
Lingering wind slabs may be reactive to human triggers on leeward aspects in the alpine.
Aspects: North, South West, West, North West.
Elevations: Alpine.
Likelihood: Unlikely - Possible
Expected Size: 1 - 2