Avalanche Forecast
Issued: Dec 12th, 2020 4:00PM
The alpine rating is , the treeline rating is , and the below treeline rating is Known problems include Wind Slabs.
shorton,
Avalanche Canada
Triggering avalanches is possible on slopes that have more than 20 cm of snow above crust and surface hoar layers.
Summary
Confidence
Weather Forecast
SATURDAY NIGHT: Partly cloudy, light southwest wind, low temperatures around -12 C.
SUNDAY: Cloudy with some light flurries in the afternoon, light southwest wind, high temperatures around -8 C.
MONDAY: Cloudy with up to 5 cm of new snow by the morning, light southwest wind, high temperatures around -5 C.
TUESDAY: Light flurries with up to 5 cm of new snow, moderate south wind, high temperatures around -8 C.
Avalanche Summary
Over the past few days there have been a few reports of small avalanches above the recently buried surface hoar and crust layers. These include several dry loose avalanches in steep terrain and a size 1 skier triggered avalanches in Glacier National Park (see the photo in this MIN report). While these avalanches have limited destructive potential, we anticipate this developing into a more concerning problem when more snow arrives.
Snowpack Summary
While there is a lot of variability across the forecast region in how the recent weather reworked the snowpack, the message is similar everywhere: assess the bond of recent snow to crusts, especially if more than 20 cm of snow is present. This is most likely at higher elevations in the Selkirks. If there is not a thick rain crust at treeline and below treeline then there is probably intact buried surface hoar.
Most areas have 10-30 cm of snow sitting above crusts. In many areas, rain and freezing rain has left a crust that extends up to 2300 m. In some areas there are multiple crusts near the surface. In areas without crusts near the surface there may be a preserved surface hoar layer.
Down near the ground remains a thick rain crust with sugary facets above and below from early November. While we have not seen recent avalanches on this layer, it continues to produce occasional hard results in snowpack tests. It may be reactive to human triggers on shallow rocky slopes in the alpine or alpine-like features at treeline.
Terrain and Travel
- Investigate the bond of the recent snow before committing to your line.
- Be careful with wind loaded pockets, especially near ridge crests and roll-overs.
- Watch for signs of instability like whumpfing, hollow sounds, shooting cracks or recent avalanches.
Problems
Wind Slabs
10-30 cm of snow that fell earlier this week may be blown into unstable slabs. In certain areas this snow may be poorly bonded to underlying layers of surface hoar and/or crusts. This is most likely a problem at treeline and alpine elevations in areas that received more than 20 cm of snow in the recent storm.
Aspects: All aspects.
Elevations: Alpine, Treeline.
Likelihood
Expected Size
Valid until: Dec 13th, 2020 4:00PM
