A capping crust has simplified our region's snowpack. Assess wind slab hazards carefully before committing to large terrain features.
New snow at higher elevations has seen extensive wind redistribution as a result of strong to extreme southwest winds. Expect to find increasingly deep and potentially reactive wind slabs as you gain elevation into the alpine. Danger is low in areas that have a solid melt-freeze crust on the surface.
Monday night: Clear. Light west winds, increasing into the morning.
Tuesday: Sunny with cloud developing in the afternoon. Light to moderate southwest winds, becoming strong at ridgetop, increasing over the day and overnight. Alpine high temperatures around -12.
Wednesday: Mainly cloudy with isolated flurries and a trace of new snow. Light to moderate southwest winds, becoming strong at ridgetop. Alpine high temperatures around -8.
Thursday: Mainly cloudy. Light west or southwest winds, easing from strong at ridgetop. Alpine high temperatures around -12.
Sunday's reports of new avalanche activity were limited to small (size 1) ski cut wind slabs, with fracture depts of 5-15 cm. These were isolated to northerly aspects at ridgetop.
Reports from Saturday in the Fernie area describe a widespread natural avalanche cycle affecting the region over Friday night, with a mix of storm slabs, wet slabs, and loose wet avalanches reaching size 3. Daytime observations were limited by weather, but several large (size 2) wet slabs were triggered with explosives in the same area. All reports have suggested only storm snow was involved in this avalanche activity, with no releases involving deeper snowpack layers.
While natural avalanche is now low in areas where a new crust has capped the snowpack, small, stubborn wind slabs now exist in areas where a bit of wind-affected snow accumulated above the crust toward the end of the storm. The region's highest alpine elevations that could have received heavy snowfall instead of rain during the storm may hold larger, deeper slabs.
Up to 50 cm of recent storm snow combined with strong to extreme southwest winds have likely formed wind slabs in the alpine and exposed treeline areas above about 2100 metres. Below this elevation, 5-10 cm of snow, also wind-affected, covers a solid new melt-freeze crust that now caps the mid and lower snowpack. In many areas this capping crust may extend to mountaintops.
The bottom 10-20 cm of the snowpack consists of faceted snow and decomposing crusts. This basal layer has not been an active avalanche problem in the region since December and would likely require a sustained warming event before re-emerging as a concern.
