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.
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.
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.
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.
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.
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.
