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 on small slopes and watch for signs of instability, overhead hazard and a buried layer of weak surface hoar.
Riders continue to be surprised by large avalanches sliding on this layer.
Summary
Confidence
Avalanche Summary
Several touchy, small to large (up to size 2.5) rider-triggered persistent slab avalanches were reported northwest of Golden in the last week. This indicates that the early December surface hoar layer is still easy to trigger in certain terrain. They have mostly occurred in treeline and alpine terrain, but have been reported as low as 1950 m. This Mountain Information Network (MIN) post from neighboring Glacier National Park is the most recent occurence.
Snowpack Summary
10 to 20 cm of recent snow and moderate southwest wind has formed windslabs over old wind-affected snow, sun crusts on steep south aspects, and surface hoar in sheltered areas. 25 to 40 cm below the snow surface, a rain crust has been observed up to 2100 m around Revelstoke, 1500 m around Mica Creek, and not at all around Blue River.
A concerning layer of surface hoar is now buried 50-80 cm deep. This layer has recently been reactive to human triggering above 1900 m.
The lower snowpack is generally faceted, but shows signs of strengthening and rounding. A hard crust may be found near the ground.
Average treeline snowpack depths are around 80-120 cm. Snowpack tapers rapidly as you move lower in elevation.
Weather Summary
Sunday Night
Mostly cloudy. Trace of snow expected. Light southwest ridgetop wind. Treeline high around -4°C. Possible temperature inversion.
Monday
Mostly cloudy. Possible trace of snow expected, up to 5 cm in the north end of the forecast area. Light south ridgetop wind. Treeline temperature around -3 °C. Possible alpine temperature inversion.
Tuesday
Cloudy. 2-5 cm of snow expected. Light south or southeast ridgetop wind. Treeline temperature around -2 °C. Possible alpine temperature inversion.
Wednesday
Cloudy. 5-10 cm of snow expected. Light to moderate southwest ridgetop wind. Treeline temperature around -3 °C.
More details can be found in the Mountain Weather Forecast.
Terrain and Travel Advice
- Make observations and assess conditions continually as you travel.
- Remote triggering is a concern, watch out for adjacent and overhead slopes.
- Carefully assess open slopes and convex rolls where buried surface hoar may be preserved.
- Carefully evaluate steep lines for wind slabs.
Problems
Persistent Slabs
A persistent weak layer of surface hoar is down 50-80 cm in the snowpack. Large, human triggered avalanches have occurred over the past few days at treeline and above.
Aspects: All aspects.
Elevations: Alpine, Treeline.
Likelihood
Expected Size
Wind Slabs
Watch for isolated pockets of reactive windslab in wind-exposed terrain. Use extra caution below ridgecrests and in cross-loaded features.
Aspects: North, North East, East, North West.
Elevations: Alpine, Treeline.
Likelihood
Expected Size
Valid until: Dec 18th, 2023 4:00PM
