Avalanche Forecast
Regions: Northwest Coastal.
Use caution as you transition into wind effected terrain. New wind slabs could be touchy. There is still some uncertainty in how the mid January layer will respond to the new load.
Confidence
Low - Uncertainty is due to the fact that persistent slabs are particularly difficult to forecast.
Weather Forecast
Friday night: moderate southerly winds in the alpine with up to 10mm of precipitation throughout the day. Low of -2 at 900m.
SATURDAY: Stormy weather continues with another 10mm of precipitation. Moderate to strong wind from the south and freezing levels rising to 1000m.
Sunday: some light flurries with light to moderate southwest winds. High of -3 at 900m.
Monday: light flurries ending in the afternoon. moderate west winds with a high of -3 at 900m.
Avalanche Summary
On Friday a very large (size 3) wind slab was triggered by a natural cornice fall. This avalanche was on a north east aspect at 1700m.
Natural glide slab avalanches continue to be observed in the region as well.
Warm weather earlier this week has resulted in a few loose wet and glide slab avalanches. The most concerning avalanche activity has been a string of persistent slab avalanches over the past week. These have occurred on a 30-50 cm deep layer of surface hoar in southern parts of the region around Terrace and Stewart. This has included both natural avalanches and human-triggered avalanches. The photos of the avalanche in this MIN report at Clague are good examples of the type of treeline elevation terrain where this problem can be found. We are uncertain whether the persistent slab problem will remain reactive after the melt freeze cycle tapers off.
Snowpack Summary
As the storm builds throughout the day on Friday new wind slab and storm slabs will develop over old refrozen surfaces in the treeline and alpine.
The below treeline and lower parts of the treeline elevation will continue to see moist snow and potentially rain as the freezing levels continue to fluctuate.
Below this is a surface hoar layer buried 30 to 50cm deep and could still be triggered at treeline in the Terrace and Stewart areas.
Terrain and Travel
- Carefully assess open slopes and convex rolls where buried surface hoar may be preserved.
- Watch for newly formed and reactive wind slabs as you transition into wind affected terrain.
- Wind slabs may be poorly bonded to the underlying crust.
Avalanche Problems
Wind Slabs
The incoming storm will likely form new wind slabs that will not bond well to the crust that covers much of the terrain. Strong winds could mean that wind slab could be found further down slope then expected.
Aspects: North, North East, East, South East, West, North West.
Elevations: Alpine, Treeline.
Likelihood: Very Likely
Expected Size: 1 - 2
Persistent Slabs
It's possible to trigger avalanches on a 30-50 cm deep surface hoar layer that has recently been reactive near Terrace and Stewart. Most avalanche activity has been at treeline elevations, but we are still uncertain about the spatial distribution of this problem.
Aspects: All aspects.
Elevations: Alpine, Treeline.
Likelihood: Possible - Likely
Expected Size: 1.5 - 2