Avalanche Forecast
Regions: Tumbler.
Exposed areas have been building up wind slabs like a production line over several stormy and very windy days. Seek out sheltered areas to avoid the hazard and enjoy softer snow. Triggering a wind slab might be the best way to cause a large and destructive step down avalanche.
Confidence
Moderate
Avalanche Summary
A helpful MIN report from Saturday in Perry Creek describes active wind slab formation conditions and a solid avoidance strategy. We suspect users who start poking into higher elevations will see evidence of a natural wind slab avalanche cycle.
Looking forward, wind slabs formed by the recent stormy weather are expected to remain reactive to human triggering over the near term.
Snowpack Summary
20-40 cm of snow gradually accumulating over the past week should now be well redistributed into lee terrain in wind-exposed areas by recent strong to extreme southwest winds.
This recent snow overlies previous wind-affected snow as well as a melt-freeze crust found on sun-exposed slopes and on all aspects below 1600 m. The bond at this interface is reportedly quite strong in the adjacent west Rockies and Cariboos but remains worthy of investigation in this region where it lies more certainly within a human triggering depth.
Several more crust/facet/surface hoar layers exist in the upper and middle portions of the snowpack, however professionals in adjacent regions are beginning to de-emphasize them. The most concerning persistent weak layer by a mile is at the base of the snowpack, composed of large and weak facets formed in November. This layer is widespread and most likely triggerable in steep, rocky alpine terrain.
In general, the snowpack is weaker and shallower in this area than in areas farther west, with an average snowpack depth of around 200 cm at treeline. This makes deep persistent slab problems in thinner snowpack areas here quite a bit more concerning.
Weather Summary
Sunday night
Cloudy with easing flurries bringing up to 5 final cm of new snow. Strong southwest winds, easing in the morning.
Monday
Mainly cloudy with isolated flurries. Moderate to strong southwest winds easing to light west over the day. Treeline high temperatures around -6.
Tuesday
Mainly sunny. Light northwest winds shifting southwest. Treeline high temperatures around -10.
Wednesday
Becoming cloudy. Moderate to strong southwest winds. Treeline high temperatures around -8.
More details can be found in the Mountain Weather Forecast.
Terrain and Travel Advice
- Be careful with wind slabs, especially in steep, unsupported and/or convex terrain features.
- Avoid steep, rocky, and wind effected areas where triggering slabs is more likely.
- Avalanche hazard may have improved, but be mindful that deep instabilities are still present.
Avalanche Problems
Wind Slabs
Strong to extreme southwest winds have transported 20-40 cm of recent storm snow, scouring windward slopes and loading leeward features with thick wind slabs. Approach all lee and cross-loaded terrain with caution.
Keep in mind that larger wind slab releases have the potential to step down to the weak basal snowpack, resulting in very large and consequential avalanches.
Aspects: North, North East, East, South East, North West.
Elevations: Alpine, Treeline.
Likelihood: Possible
Expected Size: 1 - 2
Deep Persistent Slabs
A layer of large and weak facets sits near the base of the snowpack. This layer is most prominent in upper treeline and alpine elevations. Riders are most likely to trigger an avalanche on this layer in steep terrain where the snowpack is, shallow. Your best defence is to stay diligent in choosing low-consequence terrain away from overhead exposure.
Aspects: All aspects.
Elevations: Alpine, Treeline.
Likelihood: Unlikely - Possible
Expected Size: 2 - 3.5