Avalanche Forecast
Regions: Bonnington, Kootenay Boundary, Kootenay Pass, Moyie, Norns, Rossland, South Okanagan, St. Mary, Ymir.
Watch for wind affect in unexpected places. Northerly winds will redistribute snow into wind slabs on south facing terrain features.
Continue to be wary of thin start zones and head to supported terrain.
Confidence
Moderate
Avalanche Summary
On Friday small natural and skier triggered wind slabs were reported throughout the region.
Avalanches on the persistent and deep persistent weak layers have not been reported within this region recently. However operators further north in the Selkirks continue to report natural and human triggered avalanches on these buried weak layers.
Snowpack Summary
10-20 cm of wind distributed new snow can be found at the surface, over wind effected surfaces on north facing slopes and a melt freeze on sun affected south facing slopes. The upper snowpack contains several weak layers, with up to 3 surface hoar layers in the upper 70 cm. The primary concern is the early January surface hoar (40-80 cm deep). Observations suggest that this layer is rounding and beginning to bond but may still be reactive in sheltered and shaded terrain features.
A thick melt freeze crust from Boxing Day is buried 70-100 cm deep. This layer is helping to cap our lower snowpack weaknesses but is a concern at higher elevations where this crust begins to thin and becomes less supportive.
The lower snowpack contains weak and facetted grains from November. Triggering an avalanche on this weakness is unlikely. Concern remains for heavy loads such as cornice falls, machine triggers or step down avalanches. Thin snowpack areas where weak layers sit closer to the surface should still be treated as suspect. Check out the latest forecaster blog on these deep weak layers here.
Weather Summary
Saturday Night
Mostly clear skies overnight with trace accumulations possible. Moderate northeast winds. Freezing levels below valley bottom.
Sunday
Sunny with no snowfall expected. Moderate northeast winds continue, alpine high temperatures of -15°C.
Monday
Sunny with increasing afternoon cloud. Winds switch to moderate westerlies. Alpine high of -14°C.
Tuesday
A mix of sun and cloud. Moderate westerlies. Alpine high of -10°C.
More details can be found in the Mountain Weather Forecast.
Terrain and Travel Advice
- Watch for newly formed and reactive wind slabs as you transition into wind affected terrain.
- Carefully assess open slopes and convex rolls where buried surface hoar may be preserved.
- In areas where deep persistent slabs may exist, avoid shallow or variable depth snowpacks and unsupported terrain features.
Avalanche Problems
Wind Slabs
Expect to find reactive wind slabs on south facing slope on exposed slopes. Here wind loading may sit over a crust, increasing reactivity.
Recent winds have varied throughout the region - look for wind affected snow on all aspects as you approach or descend from ridgelines. In sheltered terrain wind loading potentially sits over buried surface hoar, propagation may be wider than you expect.
Aspects: All aspects.
Elevations: Alpine, Treeline.
Likelihood: Possible - Likely
Expected Size: 1 - 2
Persistent Slabs
A persistent weak layer of surface hoar is buried 50 to 70 cm down. This depth is prime for human triggering. Buried surface hoar is more likely to be preserved in terrain features protected from wind and sun effect.
Deeper in the snowpack near the ground, the snowpack is very weak and can be triggered under the right circumstances. Be especially suspicious of shallow, rocky, or cross-loaded areas with variable snow depths.
Aspects: All aspects.
Elevations: All elevations.
Likelihood: Possible
Expected Size: 1 - 3