Wind slabs will remain reactive to human triggering on all aspects. Use caution in wind-affected terrain, especially on steep, convex slopes or roll-overs.
Wind slabs exist on various aspects in exposed terrain and around ridgelines. Last weekend's storm initially came in with southwest winds, but with the intrusion of arctic air, winds switched to the northeast, building slabs in less common locations. These slabs have formed on top of a widespread crust and may bond poorly to this hard surface.
A strong ridge of high pressure will keep the region dry and cold until Friday. Wind and snowfalls are expected for the weekend as a shift in the weather pattern will occur.
Thursday night: Partially cloudy. Alpine temperatures around -15 C. Light to moderate northwesterly winds.
Friday: Partially cloudy. Freezing level rising to 500 m. Alpine temperatures around -8 C. Light to moderate westerly winds.
Saturday: Cloudy with light snowfall. Freezing level rising to 1200 m. Alpine temperatures around -6 C. Strong to extreme southwesterly winds.
Sunday: Snow 10-15 cm. Freezing level rising to 1200 m. Alpine temperatures around -4 C. Strong to extreme southerly winds.
Thursday, snowmobilers were able to easily trigger soft wind slabs (size 1) on rollovers in open trees. Wednesday, a loose dry avalanche ran especially far after being skier-triggered on a steep convexity.
Earlier this week, shifting winds have redistributed the storm snow into wind slabs and several natural avalanches occurred. Check out our field team's MIN report from Pine Pass earlier this week.
During the peak of the storm last Saturday, several large natural storm slab avalanches were reported from treeline elevations around Kakwa.
Last weekend's storm brought 20-100 cm of new snow. Recent northeasterly winds have been redistributing this new snow into wind slabs in lee areas and creating a heavily wind-affected surface in the alpine and exposed treeline. This new snow overlies a widespread crust created from a rain event in early February. This 1-20 cm thick crust exists on all aspects and elevations.
Below the crust, 10-40 cm of more settled snow exists above the late January weak layer. This layer consists of weak faceted snow, a melt-freeze crust, and surface hoar crystals in isolated sheltered areas at treeline and below. In most areas, this layer is bridged by the thick crust above it. It is currently considered dormant, but could become active later this season.
The lower snowpack is generally strong and well-bonded. The base of the snowpack is expected to be weak and faceted in shallow, rocky slopes east of the divide.
