Fresh wind slabs will form in lee terrain features and below ridge crests. Watch for signs of instability like whumpfing, hollow sounds, shooting cracks or recent avalanches.
Strong southwest wind will continue to redistribute the recent snow and form fresh wind slabs. Be especially mindful around steep and convex openings in the trees and ridge features in the alpine. The new and recent snow may overlie a weak interface which could result in deeper and touchier than expected slabs.
A persistent slab problem formed by a crust down 90-160 cm has created a low likelihood, high consequence scenario that is difficult to forecast. Avoid likely trigger spots such as steep, rocky slopes with a shallow or thin-to-thick snowpack. Smaller storm slabs or wind slabs have the potential to step down to a deeper weak layer.
The same feature or path can slide repeatedly when the persistent weak layer gets reloaded with new snow.
Monday night: Increasing cloud coverage, trace of new snow, strong southwest wind, treeline low around -8 °C, freezing level below valley bottom.
Tuesday: Mix of sun and cloud, up to 5 cm new snow, strong southwest wind, treeline high around -3 °C, freezing level rising to 1000 m, possible inversion.
Wednesday: Mix of sun and cloud, 5-10 cm new snow, strong southwest wind, treeline high around 0 °C, freezing level rising to 1500 m, possible inversion.
Thursday: Sunny with cloudy periods, up to 5 cm new snow, strong southwest wind, treeline high around +1 °C, freezing level around 2000 m, inversion.
On Sunday, a natural size 2 wind slab avalanche that released in extremely steep terrain was observed. A few small (up to size 1.5) wind slab and dry loose avalanches were triggered by skiers.
On Saturday, several wind slab avalanches up to size 2 released naturally and were triggered by explosives. A small size 1.5 wind slab avalanche was triggered remotely by a skier.
On Friday, explosives triggered storm stab avalanches to size 2, on average 20 cm deep. A rider triggered a size 2 wind slab avalanche 30 cm deep. Skiers triggered numerous small (size 1) avalanches. A natural avalanche cycle to size 1.5 occurred Thursday-Friday night with rapid loading of new snow.
An increasing amount of large, persistent slab avalanches was reported on Sunday. Almost all the reported avalanches over the past week ran on the early December weak layer. Deeply buried persistent problems like these don't go away overnight, and it remains a serious concern.
Notable persistent slab avalanches in neighbouring regions feature in our latest blog, Photos of recent persistent slab avalanches in the southern interior.
40-60 cm of recent storm snow fell with southwesterly wind and warming temperatures. In open terrain and upper elevations, wind developed more reactive deposits around lee and convex features. An accumulated total of 40-90 cm of new and recent snow sits now over variable and potentially weak snow surfaces including widespread facets, wind affected snow, and/or surface hoar up to 3 mm in sheltered areas.
The most notable layer of concern in the snowpack is a crust that was formed in early December and is now down 90-160 cm. Activity on this layer has been sporadic. It has generally been triggered on steep, rocky slopes, with a shallow or thin-to-thick snowpack. This layer has created a low likelihood, high consequence scenario which is best managed through conservative terrain choices and disciplined backcountry travel techniques.
