Start small and watch for signs of instability or indications that new snow has settled into a reactive slab over the old snow surface on Sunday. Expect new snow to become especially touchy on southerly slopes if the sun makes an appearance.
20-30 cm of new snow is settling into storm slabs that are not expected to bond well with the previous snow surface. Wind has already been observed accelerating slab formation around ridgetop features. Snow may shed naturally as slabs or dry loose releases from slopes exposed to sunshine.
Weak snow at the bottom of the snowpack hasn't gone away, and will be an increasing concern as rapid loading and avalanches in surface layers strain the snowpack on Saturday. Evidence of deep persistent slab avalanches has been focused in the Sparwood-Elkford area over the past month. Human triggering is most likely around steep rocky terrain features, or anywhere the snowpack is thin and weak.
Saturday night: Cloudy with continuing flurries and up to 5 cm of new snow. Light to moderate southwest winds, becoming strong at ridgetop.
Sunday: Mainly cloudy with isolated flurries and a trace of new snow. Moderate southwest winds, becoming strong at ridgetop. Alpine high temperatures around -9.
Monday: Sunny. Light southwest winds. Alpine high temperatures around -8.
Tuesday: A mix of sun and cloud with cloud increasing over the day. Moderate to strong southwest winds. Alpine high temperatures around -4.
Preliminary reports from Saturday in the neighbouring Lizard Range and Flathead mainly show new snow reacting to skier traffic and explosives control as dry loose sluffs, reaching size 2. Soft slab formation was noted in wind-affected features at ridgecrest. Similar conditions are expected to exist in areas of the South Rockies that saw 20 or more cm of new snow.
Elevated avalanche danger is expected to be maintained through Sunday as the new snow settles into more consolidated storm slabs that only gradually begin bonding with the previous snow surface. Periods of sunshine may also promote natural avalanche activity.
By the time snowfall eases off Saturday night, new snow totals over the region may reach up to 30 cm. The new snow has buried recent wind slabs and wind effect in exposed terrain as well as sun crust on solar aspects and temperature crust up to 1700 m on all other aspects. The new snow is not expected to bond well with any of these surfaces over the short term.
A thick rain crust currently sits 40-80 cm below the surface and can be found up to 2100 m. Avalanche activity was last observed at the faceting interface between this crust and overlying snow on February 17. The mid-pack is well settled and strong, but the base of the snowpack contains basal facets that are most prominent in shallow rocky start zones.
