Avalanche Forecast
Issued: Dec 20th, 2022 4:00PM
The alpine rating is , the treeline rating is , and the below treeline rating is Known problems include Persistent Slabs and Wind Slabs.
trettie,
Avalanche Canada
Use extra caution at treeline where persistent slab avalanches are more likely. Make conservative decisions, even small accidents can have big consequences during periods of cold temps and short days.
Summary
Confidence
Moderate
Avalanche Summary
A few natural persistent slab avalanches up to size 2.5 were observed yesterday. These avalanches likely released on Sunday on the mid November layer at treeline.A couple of natural wind slabs up to size 1.5 were also observed in the alpine on northeast aspects on Monday.
Snowpack Summary
On Tuesday new snow and moderate winds could form new wind slab on north and east aspects. A new surface hoar layer on sheltered features and a sun crust on south facing terrain is buried down around 15cm.
The snow becomes slightly more consolidated after the above mentioned layer until around 50cm below the surface where another weak layer, created in early December, can be found. This layer is made up of surface hoar in sheltered areas and a thin sun crust in open south-facing terrain.
The layer that is still the main concern, is that of mid-November. It is made up of large surface hoar crystals, facets, and a melt-freeze crust and can be found up to 80 cm deep. This layer has been reactive at treeline between 1700 to 2200 m, on all aspects.
Below the mid-November layer is a generally weak, faceted snowpack. Snowpack depths average 80 to 160 cm in the alpine.
Weather Summary
Tuesday Night
Flurries bringing trace amounts of new snow with light northwest winds and a Low of -23 at 1800m.
Wednesday
Mostly sunny with no new snow expected. Light easterly winds and a high of -21 at 1800m.
Thursday
Mostly sunny with no new snow expected. Light variable winds and a high of -23 at 1800m.
Friday
Cloudy with around 5cm of new snow expected. Southwest winds increasing throughout the day. High of -17 at 1800m.
More details can be found in the Mountain Weather Forecast.
Terrain and Travel Advice
- Watch for newly formed and reactive wind slabs as you transition into wind affected terrain.
- Carefully assess open slopes and convex rolls where buried surface hoar may be preserved.
- Be aware of the potential for surprisingly large avalanches due to deeply buried weak layers.
- Don't let the desire for deep powder pull you into high consequence terrain.
Problems
Persistent Slabs
There are now two persistent weak layers within the snowpack.
A 35 - 45 cm soft slab sits above a weak layer of surface hoar on shaded aspects and crust on steep solar aspects. A second weak layer of surface hoar and facets from mid-November is buried down 50 to 80cm in the region.
While avalanche activity has tapered off on these layers they likely remain rider triggerable in specific sheltered terrain features at treeline and below.
Aspects: All aspects.
Elevations: All elevations.
Likelihood
Expected Size
Wind Slabs
Moderate southwest winds will likely have formed wind slab on north and east aspects at treeline and above throughout the day on Tuesday. At treeline where wind slabs could have formed over surface hoar they may be more sensitive to rider triggering.
Be aware of the potential for wind slab avalanches to step down to deeper layers.
Aspects: All aspects.
Elevations: Alpine, Treeline.
Likelihood
Expected Size
Valid until: Dec 21st, 2022 4:00PM
