Avalanche Forecast
Issued: Feb 8th, 2021 4:00PM
The alpine rating is , the treeline rating is , and the below treeline rating is Known problems include Persistent Slabs and Wind Slabs.
astclair,
Avalanche Canada
Triggering avalanches may be possible in specific wind-drifted features or in isolated open glades near treeline where a buried weak layer persists. Monitor for these conditions where you travel.
Summary
Confidence
Weather Forecast
Brrrrrr! Cold and dry conditions persist under arctic air
Monday night: Mostly clear, light northwest wind, alpine temperature -25 C.
Tuesday: Mostly clear, light variable wind, alpine high temperature -22 C.
Wednesday: Mix of sun and cloud, light northwest wind, alpine high temperature -26 C.
Thursday: Mainly sunny, light northeast wind, alpine high temperature -24 C.
Avalanche Summary
Several small to large (size 1-3) natural and human triggered wind slab avalanches were reported over the weekend. These avalanches released on northeast through east through south aspects above 2000 m and broke 10-30 cm deep. A few of these wind slabs were triggered by cornice falls.
On Thursday, a large (size 2) skier-triggered persistent slab avalanche was reported near the Gorge area. This avalanche failed on a widespread layer of surface hoar buried 60 cm deep. While activity on this layer has decreased, there were many reports of avalanches on this layer last week. Check out these examples from the Gorge and from Corbin Pass. As a low probability/high consequence scenario, this avalanche problem warrants assessment in specific areas.
Numerous small (size 1-1.5) loose dry avalanches in unconsolidated snow have been reported in steep terrain.
Snowpack Summary
Up to 35 cm of low density snow over the past few days has combined with intermittent northwest winds to create wind slabs which may be possible to human trigger in specific lee features. In sheltered areas, cohesion-less powder may be prone to dry loose avalanches that can run far and fast in these cold, dry conditions. With clear skies, steep slopes in direct sun could potentially warm midday despite the cold temperatures, and a sun crust could develop.
60-100 cm of snow from the past week is settling over a reactive weak layer of surface hoar. Reactivity on this layer has primarily been observed at treeline and in "treeline-like" features that are below treeline. Snowpack tests results continue to show the potential for propagation on this layer, like this MIN report from Sunday.
A less reactive layer of surface hoar or facets buried in early January can be found down 80-130 cm.
The mid/lower snowpack is generally well settled and strong.
Terrain and Travel
- Avoid open slopes and convex rolls at and below treeline where buried surface hoar may be preserved.
- Stay off recently wind loaded slopes until they have had a chance to stabilize.
- Be aware of the potential for loose avalanches in steep terrain where snow hasn't formed a slab.
Problems
Persistent Slabs
A weak layer of surface hoar is buried 60-100cm deep on sheltered slopes near and below treeline that may be possible to human trigger.
Aspects: All aspects.
Elevations: Treeline, Below Treeline.
Likelihood
Expected Size
Wind Slabs
Intermittent ridgetop winds have redistributed the low density snow into wind slabs on lee features at upper elevations that may be possible to human trigger.
Aspects: North, North East, East, South East, South.
Elevations: Alpine, Treeline.
Likelihood
Expected Size
Valid until: Feb 9th, 2021 4:00PM
