Wind slabs will form in lee terrain features and below ridges with moderate to strong southwest wind. Be alert to conditions that change with elevation and wind exposure.
Moderate to 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.
Sunday night: Clear, moderate to strong southwest wind, treeline low around -10 °C.
Monday: Sunny, moderate to strong southwest wind, treeline high around -6 °C.
Tuesday: Mix of sun and cloud, up to 5 cm new snow, strong southwest wind gusting to extreme, treeline high around -3 °C.
Wednesday: Mix of sun and cloud, 5-10 cm new snow, strong southwest wind gusting to extreme, treeline high around 0 °C.
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 Thu-Fri night with rapid loading of new snow.
On Wednesday, evidence of a natural storm slab avalanche cycle size 1-2 was observed, likely having run during the storm earlier in the week. Wind slabs continued to be reactive near Invermere into Tuesday, up to size 2. By Wednesday, avalanche activity was predominantly loose dry entraining mass to size 1.5-2.
Last Tuesday just east of the region in the Rockies near Invermere, a size 3.5 (very large) persistent slab avalanche was triggered remotely by a skier on an alpine ridgetop. The resulting crown was 2-3 m deep and the avalanche ran about 1 km to the valley bottom. More details in this MIN report. This and other notable persistent slab avalanches in neighboring 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.
