Avalanche activity has slowed down, but there is a lingering potential to trigger large avalanches on buried weak layers. Read about managing these conditions in this forecaster blog.
Despite decreasing avalanche danger, there remains a lingering possibility to trigger persistent slab avalanches in isolated steep terrain features. The primary layer of concern is layer of surface hoar, facets, and/or crusts buried 30-60 cm deep throughout the region.
Brrrrrr! Cold and dry conditions persist under arctic air...
THURSDAY NIGHT: Clear skies, light northeast wind, treeline temperatures drop to -30 C.
FRIDAY: Sunny, light northeast wind, treeline temperatures around -20 C.
SATURDAY: Sunny with a few clouds, light to moderate east wind, treeline temperatures around -18 C.
SUNDAY: Sunny with a few clouds, light wind, treeline temperatures around -15 C.
Minimal avalanche activity has been reported since the cold weather arrived on Monday.
Last weekend there were a few reports of large avalanches (size 2.5-3) on southeast aspects in the alpine. These avalanches released naturally, possibly due to the influence of solar radiation or cornice falls. See a photo here. A large human triggered avalanche (size 2.5) on buried surface hoar was last reported near Quartz Creek on Feb 3, and a small (size 1) explosive triggered avalanche on surface hoar was reported on Monday. While there is an overall trend in decreasing likelihood of avalanches, there still remains a lingering possibility to trigger a persistent slab avalanche in isolated steep terrain features.
The upper snowpack is becoming soft and faceted with the cold temperatures, while recent wind has left some isolated wind slabs in lee features. A weak layer formed in late January and is now 30-60 cm deep. In the northern Purcells this layer has been reported as a surface hoar layer at treeline and below treeline elevations, but a combination of facets on crusts could exist at all elevations throughout the region. This persistent weak layer has potential to surprise backcountry users with how wide the fracture can travel across slopes. This layer will be slow to gain strength and requires careful terrain selection. The northern Purcells also have an older surface hoar layer that can still be found 60-100 cm deep at treeline. Additional weak layers may exist near the bottom of the snowpack, and should be considered in steep rocky areas with a shallow or thin to thick snowpack.
