Avalanche Forecast
Issued: Dec 15th, 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
Choose mellow slopes, and watch for signs of instability 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 skier-triggered persistent slab avalanches up to size 2.5 were reported over the week, including one on Thursday, northwest of Golden. They have mostly occurred in treeline terrain, but have been reported as low as 1950 m. They failed on weak layers comprised of surface hoar and or facets 40-70 cm below the snow surface. Check out this MIN from the adjacent region. It paints a clear picture.
Human-triggered persistent slabs remain the primary concern.
Snowpack Summary
10 to 20 cm of new snow has buried old wind-affected snow, sun crusts on steep south aspects and surface hoar. Approximately 25 to 40 cm down exists a rain crust that has been observed to ridgeline in most areas.
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 a mix of rounded and faceted grains. A hard crust may be found near the ground.
Treeline snowpack depths are variable and generally range between 100 to 150 cm. Snowpack tapers rapidly as you move lower in elevation.
Weather Summary
Friday Night
Cloudy. 5-10 cm of snow expected. Moderate to strong southwest ridgetop wind. Treeline temperature around -4°C. Freezing level around 1000 m. Possible weak alpine temperature inversion.
Saturday
Cloudy. 2-5 cm of snow expected. Light southwest ridgetop wind. Treeline temperature around -3°C. Freezing level around 1000 m, possibly rising as high as 1500 m in the north end of the forecast area.
Sunday
Partly cloudy. No new snow expected. Light variable ridgetop wind. Treeline temperature around -6°C. Possible weak alpine temperature inversion.
Monday
Mostly cloudy. Possible trace of snow expected. Light to moderate southeast ridgetop wind. Treeline temperature around -3 °C. Possible alpine temperature inversion.
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.
- Make observations and assess conditions continually as you travel.
- Carefully assess open slopes and convex rolls where buried surface hoar may be preserved.
- Be especially cautious near rock outcroppings, on steep convexities and anywhere the snowpack feels thinner than average.
Problems
Persistent Slabs
A persistent weak layer is down 50-80 cm in the snowpack. Large, human triggered avalanches have occurred over the past few days above treeline.
Aspects: All aspects.
Elevations: Alpine, Treeline.
Likelihood
Expected Size
Wind Slabs
Moderate southwest winds and fresh snow continue to form reactive wind slabs. Use extra caution below ridgecrests and in cross-loaded features.
Aspects: North, North East, East, West, North West.
Elevations: Alpine, Treeline.
Likelihood
Expected Size
Valid until: Dec 16th, 2023 4:00PM
