Flurries and wind will continue to build slabs, expect to find the most reactivity in areas with heavy snowfall deposits or gusty winds.
A layer of weak facets (sugary snow) can be found down 50-90 cm over a crust that formed in early December. This layer has produced large avalanches from explosive triggers and has shown reactivity in snowpack tests. The new snow may add enough stress to trigger a persistent slab.
Ongoing snowfall and strong winds means ongoing slab development. Slabs will be more reactive on leeward (wind-loaded) slopes where deposits are deeper and stiffer. Be mindful of loose-dry sluffing in steeper wind-sheltered terrain.
Light to heavy snowfall is expected across southern BC Friday night through Sunday. An easterly arctic front meeting a southwesterly flow will produce enhanced snowfall where this clash occurs; a band of heavy snowfall is forecasted from Waterton, through Fernie, and into the western South Rockies, possibly clipping the Castle area.
Friday night: Snow, 5-15 cm by Saturday morning, Winds southerly gusting to 30 km/hr. Treeline temperatures dropping to -20.
Saturday: Continued snow with another 5-15 cm through the day. Moderate southwest wind. Treeline temperatures near -12 and temperatures dropping.
Sunday: Cloudy with isolated flurries, up to 5-10 cm. Light winds from the southwest and colder temperatures at -25.
Monday: Mix of sun, cloud, and isolated flurries. Light, gusty winds and cold temperatures with a high of -19.
On Friday, strong winds impacting new snow likely encouraged reactive slabs to form.
On Thursday, explosives triggered a few small (size 1) storm slab avalanches. On Wednesday, the South Rockies field team reported several wind slabs that appeared to have slid on the early December crust and up to size 2.
Another 15-30 cm Friday brought recent snowfall totals upwards of 50 cm with more expected through the weekend. Gusty winds have produced variable storm slabs and cross-loaded terrain features. In some wind exposed areas surfaces have likely been stripped back down to older wind slabs and the early December crust. Sheltered areas may still hold loose snow. A lot of variability exists.
Below the new snow and wind slabs, a well-consolidated upper snowpack overlies a substantial crust from early December. This crust is approximately 50-90 cm below the surface, 20 cm thick on average, and is present across all aspects to at least 2400 m. A layer of weak facets (sugary snow) has been reported above this crust. Snowpack tests are generally showing hard results on this interface, however, areas, where avalanches have recently failed on this crust, continue to be problematic once reloaded with new snow.
Below 2300 m, several early-season crusts make up the lower snowpack. Snowpack depths range from 80-150 cm at treeline elevations and taper quickly below 1900m.
