Regions
Kootenay Boundary.
Continue making conservative terrain choices this weekend and be wary of any slope that did not slide during the last storm.
Weather Forecast
Synopsis: The ridge of high pressure gives way to weak upper trough on Saturday bringing more cloud and unsettled conditions through Sunday. We could see flurries on the weekend but no significant accumulation. Ridge winds are generally light or moderate from the W-NW. The ridge should rebuild on Monday bringing drier conditions and more sunshine. The freezing level remains at valley bottom throughout the period.
Avalanche Summary
Further evidence of the widespread and large natural avalanche cycle was reported on Thursday. Avalanches up to size 3 were reported from all aspects at all elevations. Conditions remained touchy to skier triggered on Thursday, particularly around Rossland. There is an interesting report from Mount Kirkup (west of Rossland) where an experienced observer describes this as one of the most active avalanche periods they have seen in the region. They remotely triggered one slab from 20 degree terrain and observed other naturals occurring on relatively low angle slopes.
Snowpack Summary
The current snow surface consists of a melt-freeze crust with surface hoar on top in sheltered areas. This crust is reported on aspects to ridge top in some areas and below 1800 m in others. Fresh wind slabs are likely in exposed alpine and treeline terrain. The main snowpack concern is a buried surface hoar layer (down 80-100 cm), which is sitting on a rain crust in some places. This widespread persistent weakness exists at all elevation bands and remains a concern for triggering. At the base of the snowpack, a crust/facet combo appears to have gone dormant for the time being.
Problems
Persistent Slabs
Persistent Slab avalanches are the release of a cohesive layer of snow (a slab) in the middle to upper snowpack, when the bond to an underlying persistent weak layer breaks. Persistent layers include: surface hoar, depth hoar, near-surface facets, or faceted snow. Persistent weak layers can continue to produce avalanches for days, weeks or even months, making them especially dangerous and tricky. As additional snow and wind events build a thicker slab on top of the persistent weak layer, this avalanche problem may develop into a Deep Persistent Slab.
Storm Slabs
Storm Slab avalanches are the release of a cohesive layer (a slab) of new snow that breaks within new snow or on the old snow surface. Storm-slabs typically last between a few hours and few days (following snowfall). Storm-slabs that form over a persistent weak layer (surface hoar, depth hoar, or near-surface facets) may be termed Persistent Slabs or may develop into Persistent Slabs.