Avalanche Forecast
Issued: Dec 17th, 2023 4:00PM
The alpine rating is , the treeline rating is , and the below treeline rating is Known problems include Persistent Slabs and Wind Slabs.
bchristie,
Avalanche Canada
Start with small slopes, and gather information before entering committing terrain.
Continue to be wary of a buried layer of surface hoar. The crust that was shielding it is getting weaker.
Summary
Confidence
Avalanche Summary
On the weekend the only reported avalanches were loose in steep terrain, and wind slabs and cornices controlled by explosives. These avalanches were all small.
The surface hoar continues to cause concerning results in snowpack tests, and shows signs of instability like whumpfs and shooting cracks. Despite a lack of avalanche observations, we presume that large, human triggered avalanches are still possible in areas where the crust over it is thin or non-existent.
Snowpack Summary
10-15 cm of recent snow has been redistributed by moderate southwest wind. This sits on old wind slabs, and sun crusts on steeper south aspects, and in areas sheltered from the wind, 5-30 mm surface hoar.
Down 30-50 cm a 5-15 cm thick, frozen crust exists. It has been observed up to 2350 m, but it is starting to break down at treeline and above, where it is thinner. A concerning layer of surface hoar buried in early December is 60-90 cm deep at treeline and above.
The lower snowpack is generally faceted, but is also moist in some areas in the south end of the forecast area.
Average treeline snowpack depths are between 80 and 150 cm. Snowpack depth tapers rapidly with elevation.
Weather Summary
Sunday Night
Mostly clear. No new snow expected. Light southwest ridgetop wind. Treeline high around 2°C with above freezing layer.
Monday
Mostly cloudy. Possible trace of snow expected. Light to moderate south ridgetop wind. Treeline temperature around 2°C with above freezing layer.
Tuesday
Cloudy. 2-5 cm of snow expected. Light to moderate south or southeast ridgetop wind. Treeline temperature around -3°C with alpine temperature inversion.
Wednesday
Cloudy. 5-10 cm of snow expected. Light to moderate southwest ridgetop wind. Treeline temperature around -1°C with alpine temperature inversion.
More details can be found in the Mountain Weather Forecast.
Terrain and Travel Advice
- Carefully assess open slopes and convex rolls where buried surface hoar may be preserved.
- Use conservative route selection and resist venturing out into complex terrain.
- Avalanche hazard may have improved, but be mindful that deep instabilities are still present.
- Approach lee and cross-loaded slopes with caution.
Problems
Persistent Slabs
A persistent weak layer of surface hoar is buried down 60-90 cm in the snowpack. A frozen crust was reducing the chance of triggering this layer, but it has started to break down and get weaker.
Aspects: All aspects.
Elevations: Alpine, Treeline.
Likelihood
Expected Size
Wind Slabs
Potentially most reactive with above 0 temperatures around treeline, in areas where windslab sits on a layer of weak, feathery surface hoar crystals buried in mid December.
Aspects: North, North East, East, North West.
Elevations: Alpine, Treeline.
Likelihood
Expected Size
Valid until: Dec 18th, 2023 4:00PM
