Avalanche Forecast
Issued: Jan 22nd, 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
Avalanche hazard is improving, but triggering avalanches in specific or isolated terrain remains possible. Be wary of residual reactivity in wind slabs that may be sitting over a weak layer.
Summary
Confidence
Weather Forecast
Friday night: Clear, northerly wind 20-30 km/h, treeline temperatures around -10.
Saturday: Sunny, northwest wind 20-30 km/h, treeline temperatures around -12.
Sunday: Increasing cloud, flurries starting in the afternoon, light southwest wind, treeline temperatures around -12.
Monday: Flurries, up to 5 cm, light southerly wind, treeline temperatures around -12.
Avalanche Summary
A few small skier controlled wind slabs have been reported at wind loaded ridgecrests, likely failing on shallow surface hoar and running on a near surface crust.
Last week 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
The upper snowpack is composed of an arrangement of one or more crusts, varying with elevation and between areas within the region. The uppermost crust extends up to around 2000 m, ie. ridgetop in areas such as Rossland. In higher terrain, 10-15 cm of wind affected snow may sit over crust or large surface hoar crystals in wind sheltered areas above the crust elevation.
A layer of surface hoar may be found 20-50 cm below the surface in isolated areas in the north and east of the region. There was previous avalanche activity on this layer, but it seems at this point that most features that would run, have run on it already. Where it has been found in the most recent snow profiles, it has been producing moderate to hard planar test results but the crystals are observably rounding. We expect that this layer won't be a problem for too much longer...
A couple of crusts surrounded by weak faceted grains 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 earlier this month near Rossland. More recently, some large cornice falls have have been good slope testers, some triggering 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
- Watch for wind-loaded pockets especially around ridgecrest and in extreme terrain.
- Carefully assess open slopes and convex rolls where buried surface hoar may be preserved.
- Surface hoar distribution is highly variable. Avoid generalizing your observations.
- When a thick, melt-freeze surface crust is present, avalanche activity is unlikely.
Problems
Wind Slabs
Wind slabs may be triggerable 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 the north and east of the region. Avalanche activity on this layer has dwindled over the past week. Where it has been found in snow profiles, it has been producing moderate to hard planar test results but crystals appear to be rounding. You can dig down and investigate whether the problem exists in a likely location in your riding area (wind sheltered with a sky view, north facing, treeline elevation).
Aspects: North, North East, North West.
Elevations: Treeline.
Likelihood
Expected Size
Valid until: Jan 23rd, 2021 4:00PM
