The primary concern is that superficial slabs could step down to the deep, persistent weakness, resulting in full-depth avalanches.
Moderate to strong S and SW winds over Christmas built wind slabs 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.
Friday, ski hills reported some explosive-triggered avalanches to size 2, and a few involved wind slabs that stepped down to deeper layers.
Observations from Thursday reported natural and skier-triggered avalanches to size 2 near Lake O'Hara and Bow Summit.
Earlier in the week, when the winds were stronger, there were some reports of naturals to size 3 (Grand Daddy couloir) and explosive-triggered wind slab avalanches to size two, stepping down to lower layers.
15-30 cm of storm snow from the past week, combined with strong W/SW winds, has formed wind slabs in alpine lee areas which extend 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.
Saturday: sunny skies with highs around -8C and moderate ridgetop wind.
Sunday: mix of sun and cloud, light winds, and highs around -8C.
No snow in the forecast.
See the attached table for more details (tonight is Frisday night, tomorrow is Saturday and Day 2 is Sunday)
