Avalanche Forecast
Issued: Jan 20th, 2021 4:00PM
The alpine rating is , the treeline rating is , and the below treeline rating is Known problems include Wind Slabs and Persistent Slabs.
ahanna,
Avalanche Canada
Wind slabs may remain triggerable. Be careful in drifted areas and assess open slopes and rollovers where a weak layer may be preserved.
Summary
Confidence
Weather Forecast
Wednesday night: Partly cloudy, light wind, freezing level valley bottom.
Thursday: Mix of sun and cloud, light wind, treeline temperatures around -8 C.
Friday: Sunny, light wind, treeline temperatures around -10 C.
Saturday: Sunny, light to moderate northwest to southwest wind, treeline temperatures around -13 C.
Avalanche Summary
In the last few days, skiers have triggered a few small wind slabs (size 1) at wind loaded ridgecrests.
Since last week's storm a few natural avalanches are suspected to have run on the surface hoar 20-50 cm down, including a size 2.5 storm slab out of a northwest facing gully feature around 2000 m near Nelson.
Snowpack Summary
Previous wind has likely redistributed 10-15 cm of recent snow into wind slabs in lee terrain features at upper elevations. This snow may sit over a widespread crust that extends up to around 2000 m, or large surface hoar crystals in wind sheltered areas above the crust elevation. In areas such as Rossland, the thick crust caps the snowpack to mountaintop, making travel difficult.
A layer of surface hoar may be found 20-50 cm below the surface, particularly in areas around Nelson. Some recent avalanches have run on this layer and where it has been found in snow profiles, it has been producing moderate to hard planar test results.
A couple of crusts with weak faceted grains overtop are buried deep within the snowpack. The upper layer is 80 to 130 cm deep and the lower is near the ground. A few large avalanches ran naturally on these layers last week near Rossland. More recently, some large cornice falls have have been good slope testers. Some triggered storm slabs but none stepped down to these deeper layers. While this is a good indicator for stability, the potential may linger for triggering a deep slab in steep, rocky, thin snowpack areas.
Terrain and Travel
- Be careful with wind slabs, especially in steep, unsupported and/or convex terrain features.
- Carefully assess open slopes and convex rolls where buried surface hoar may be preserved.
- When a thick, melt-freeze surface crust is present, avalanche activity is unlikely.
Problems
Wind Slabs
Previous strong wind has likely redistributed small amounts of recent snow into wind slabs in lee terrain features at upper elevations. They could remain reactive where they sit over a rain crust or large surface hoar crystals.
Aspects: North, North East, East, South East.
Elevations: Alpine, Treeline.
Likelihood
Expected Size
Persistent Slabs
Reports suggest some slopes at treeline have a weak layer of surface hoar 20-50 cm below the surface, particularly in areas around Nelson. An avalanche cycle cleaned out this layer in many areas, but in places where avalanches have not yet run, it remains a concern. Where it has been found in snow profiles, it has been producing moderate to hard planar test results. Use caution around convexities in open trees.
Aspects: All aspects.
Elevations: Treeline.
Likelihood
Expected Size
Valid until: Jan 21st, 2021 4:00PM
