Avalanche Forecast
Issued: Feb 9th, 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.
ahanna,
Avalanche Canada
Triggering avalanches may be possible in specific wind-drifted features or on open slopes near treeline where a buried weak layer persists.
Summary
Confidence
Weather Forecast
Brrrrrr! Cold and dry conditions persist under arctic air
Tuesday night: Partly cloudy with a few flurries, light westerly ridgetop wind, alpine high temperature -22 C.
Wednesday: Mix of sun and cloud, light northerly wind, alpine high temperature -26 C.
Thursday: Sunny, light to moderate northeast ridgetop wind, alpine high temperature -28 C.
Friday: Sunny, moderate easterly ridgetop wind, alpine high temperature -20 C.
Avalanche Summary
Several small to large (size 1-3) natural, human and machine triggered wind slab avalanches were reported over the last few days. 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, this weak layer warrants assessment in open, sheltered slopes at treeline where this layer is likely pronounced and preserved.
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 weekend 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, there is uncertainty as to how much direct sun on Tuesday might warm steep slopes midday given the frigid temperatures.
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 north in the region on 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 10th, 2021 4:00PM
