A suspicious layer of surface hoar is buried under the new snow, and responsible for recent avalanches - dig down and investigate the slab properties of the new snow and bond with the old surface.
A layer of weak facets (sugary snow) can be found down 60-100 cm over a crust that formed in early December. This layer has shown some reactivity in snowpack tests. The new snow may add enough stress to trigger a persistent slab.
Recent slab avalanches have failed with the new snow bonding over a layer of surface hoar. With ongoing flurries and gusty winds, slab avalanches may continue to be reactive to human triggers especially on leeward (wind-loaded) slopes that host thicker and stiffer slabs. 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 to clip the Kootenay Pass area.
Friday Night: Flurries, 10-20 cm new snow overnight, Kootenay pass is expected to see the deepest deposits. Moderate and gusty southerly winds. Treeline temperatures near -10 and freezing level at valley bottom.
Saturday: Ongoing scattered flurries, 5-10 cm. Moderate gusty southerly winds. Treeline temperatures near -10 and freezing levels at the valley bottom.
Sunday: Cloudy and flurries, up to 7-12 cm. Light winds from the southwest and colder temperatures at -13.
Monday: Cloudy with sunny breaks. Light winds from the southwest and colder temperatures at -13.
On Thursday, several natural and skier-controlled storm slab avalanches up to size 2 were reported, and explosives triggered slab avalanches to size 2.5; avalanches ranged from 20-60 cm deep.
20-40 cm of recent storm snow overlies a thin freezing rain crust and a surface hoar interface. Recent westerly winds have pressed surfaces and loaded leeward features.
The upper snowpack overlies a substantial crust from early December. This crust is approximately 70-100 cm below the surface, 10 cm thick on average, and is present across all aspects to at least 2300m. A layer of weak facets (sugary snow) has been reported above this crust.
The lower snowpack is composed of several early-season crusts. Snow depths at treeline average 150-200 cm. Below 1800 m the snowpack remains relatively shallow with 80-120 cm on average. The deepest snowpack can be found in the Kootenay Pass area.
