Avalanche Forecast
Issued: Dec 21st, 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.
Check out this blog from our Yukon field team about managing the cold while traveling in avalanche terrain.
Summary
Confidence
Avalanche Summary
On Tuesday several size one skier triggered wind slab avalanches were reported. These avalanches were on easterly aspects at upper treeline.
A few natural persistent slab avalanches up to size 2.5 were observed on Monday. . 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
Variable wind effect can be found in alpine and upper treeline. 10 to 25cm of recent unconsolidated storm snow overlies a layer of surface hoar in all sheltered terrain and a sun crust on south facing terrain.
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.
The snowpack is becoming increasingly complex and faceted.
Weather Summary
Wednesday Night
No new snow expected. Light northeast winds and a low of -29 at 1800m.
Thursday
Mostly sunny with no new snow expected. Light westerly winds and a high of -22 at 1800m.
Friday
Cloudy with around 5cm of new snow expected. Southwest winds increasing throughout the dayto strong by the afternoon. High of -16 at 1800m.
Saturday
Stormy with around 10cm of new snow expected. Strong southwest winds and a high of -7 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 three persistent weak layers within the snowpack.
The first is only recently just been buried , it is currently not a concern as the snow above has not formed a slab. It is a surface hoar layer in sheltered terrain and a crust on south facing slopes.
The second is a weak layer of surface hoar on shaded aspects and crust on steep solar aspects found down around 50cm.
The third is a layer of surface hoar and facets from mid-November which is buried down around 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
Wind effect can be observed on all aspects at treeline and above. The largest and most sensitive wind slabs will be found on easterly slopes at upper elevations. 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 22nd, 2022 4:00PM
