Avalanche Forecast
Regions: Banff, Banff Yoho Kootenay, East Side 93N, Field, Kootenay, LLSA, Lake Louise, Little Yoho, Sunshine, West Side 93N.
Our primary avalanche concern is that superficial slabs could step down to the deep, persistent weakness resulting in full-depth avalanches.
The thinner and rockier the terrain, the higher probability of triggering an avalanche.
Confidence
Moderate
Avalanche Summary
Explosive work on Sunday triggered a size 2.5 avalanche in the Yoho region, failing on the deep persistent avalanche problem. Reports of avalanches failing on the deep persistent problem have been received almost daily over the past two weeks. Local ski hills also reported triggering wind slabs up to size 2 with explosive control work.
Snowpack Summary
15-30 cm of recent snow, combined with strong W/SW winds, has formed widespread wind slabs in the alpine and down into treeline.
The mid and lower snowpack is faceted and weak, with facet/crust interfaces near the ground. This is more pronounced east of the divide, while western regions display a deeper more settled snowpack.
Snowpack depths at tree-line are about 60 cm in eastern areas and 100 cm west of the divide.
Weather Summary
Scattered flurries beginning on Monday, with snow accumulation expected to range from a trace to 5 cm by Wednesday. Winds will increase to moderate from the northwest on Monday morning and remain elevated through the start of the week. Freezing levels will stay at the valley bottom, as a cooling trend continues throughout the week.
Terrain and Travel Advice
- Avoid thin areas like rocky outcrops where you're most likely to trigger avalanches on deep weak layers.
- Avoid freshly wind-loaded features, especially near ridge crests, rollovers, and in steep terrain.
- Pay attention to cornices and give them a wide berth when traveling on or below ridges.
Avalanche Problems
Deep Persistent Slabs
Weak facets and depth hoar associated with crusts near the base of the snowpack have resulted in avalanches 60-100 cm deep. Any area with a stiffer slab over the facetted lower snowpack can generate a larger avalanche that steps down to the ground.
Aspects: All aspects.
Elevations: Alpine, Treeline.
Likelihood: Possible
Expected Size: 1.5 - 3
Wind Slabs
Moderate to strong W and SW winds over the past week promoted cornice development and built wind slabs and in lee features in the alpine and down into treeline. These slabs are a concern where they sit over weak facets that could "step down" to the basal layers.
Aspects: All aspects.
Elevations: Alpine, Treeline.
Likelihood: Possible
Expected Size: 1 - 1.5