Avalanche Forecast
Issued: Dec 23rd, 2020 4:00PM
The alpine rating is , the treeline rating is , and the below treeline rating is Known problems include Wind Slabs and Persistent Slabs.
mconlan,
Avalanche Canada
The alpine is unseasonably warm, which may make slabs easy to trigger.
Summary
Confidence
Moderate - Uncertainty is due to how the snowpack will react to the forecast weather.
Weather Forecast
WEDNESDAY NIGHT: Clear skies, 20 to 40 km/h southwest wind, alpine temperature -1 C, above-freezing layer around 2000 m in the south of the region.
THURSDAY: Clear skies, 30 to 50 km/h southwest wind, alpine temperature 0 C, above-freezing layer dissipating by the end of the day in the south of the region.
FRIDAY: Increasing clouds, 20 km/h south wind, alpine temperature -1 C.
SATURDAY: Cloudy with snowfall, accumulation 5 cm, 20 km/h south wind, alpine temperature -5 C.
Avalanche Summary
We received reports of the recent storm snow forming reactive slabs on Wednesday at treeline and alpine terrain.
A few persistent slab avalanches were triggered in the north of the region in the past few days, near the Hurley. They were triggered by riders, heavy machinery, and naturally. The slabs were generally 60 to 90 cm deep, around 2000 m, and released on the weak layers described in the snowpack summary.
Snowpack Summary
Around 60 cm of snow fell near Coquihalla and Manning Park on Monday and 15 cm accumulated near Duffey Lake. Since then, strong wind from variable directions has formed wind slabs in exposed terrain up high. Warm air is forecast for the alpine and particularly for the south of the region, which could mean that these slabs may remain easy to trigger.
A hard melt-freeze crust from early December is found around 40 to 120 cm deep in the snowpack. This crust may have weak layers above it, consisting of feathery surface hoar or sugary faceted grains. These weak layers do not appear to be prevalent in the south of the region but may be found in the north (e.g., Duffey Lake, Hurley). The snowpack should be treated as suspect anywhere you find either surface hoar or faceted grains above the crust.
The remainder of the snowpack is well-settled in the south of the region. In the north, another melt-freeze crust with associated faceted grains around it may be found near the ground. Without evidence of recent avalanche activity, the layer appears to be dormant at this time.
Terrain and Travel
- Avoid steep slopes when air temperatures are warm, or solar radiation is strong.
- Be careful as you transition into wind affected terrain.
- Give the new snow several days to settle and stabilize before pushing into bigger terrain.
- Potential for wide propagation exists, fresh slabs may rest on surface hoar, facets and/or crust.
Problems
Wind Slabs
Wind slabs likely exist in steep and exposed terrain and they remain likely to trigger during this warm period at higher elevations. In sheltered terrain, the recent snow may also still be reactive to riders until it bonds to the snowpack.
Aspects: All aspects.
Elevations: Alpine, Treeline.
Likelihood
Expected Size
Persistent Slabs
Weak layers of surface hoar and/or faceted grains may be found above a hard melt-freeze crust. Recent reports suggest the weak layers may be less prevalent in the south of the region, but they may still exist in localized pockets. There is uncertainty in how warm alpine air will affect the snowpack. It is possible that the warming may increase the potential of humans triggering these layers.
Aspects: All aspects.
Elevations: All elevations.
Likelihood
Expected Size
Valid until: Dec 24th, 2020 4:00PM
