Avalanche Forecast
Issued: Dec 21st, 2019 4:00PM
The alpine rating is , the treeline rating is , and the below treeline rating is Known problems include Storm Slabs and Persistent Slabs.
mconlan,
Avalanche Canada
The powerful storm is still impacting the region, continuing the avalanche cycle. Triggering of avalanches will remain very likely on Sunday. Travel in avalanche terrain is not recommended.
Summary
Confidence
Weather Forecast
SATURDAY NIGHT: Cloudy with snowfall, accumulation 15 to 25 cm, strong southwest wind, alpine temperature -4 C, freezing level 1500 m.
SUNDAY: Cloudy with snowfall, accumulation 5 to 10 cm, light to moderate southwest wind, alpine temperature -4 C, freezing level 1400 m.
MONDAY: Cloudy with snowfall, accumulation 5 to 10 cm, light to moderate southwest wind, alpine temperature -5 C, freezing level 800 m.
TUESDAY: Mix of sun and cloud with isolated flurries, light southwest wind, alpine temperature -8 C, freezing level below valley bottom.
Avalanche Summary
Many large storm slab and persistent slab avalanches were triggered naturally, by humans, and by explosives on Friday and Saturday. This trend is expected to continue on Sunday with stormy conditions.
Snowpack Summary
The storm has already dropped over 50 to 80 cm of snow and will continue to hammer the region with about 20 cm of snowfall tonight and another 10 cm on Sunday. This snow will load multiple weak layers, including:
- a feathery surface hoar layer buried around 50 to 100 cm beneath the new snow.
- a surface hoar layer buried about 80 to 120 cm, with an associated melt-freeze crust on steep south aspects.
- a complex layer of weak and sugary faceted snow, surface hoar, and melt-freeze crusts in the bottom half of the snowpack.
Given the weak nature of these layers, both natural and human-triggered avalanches will remain very likely to trigger given the substantial amount of new snow and strong wind forecast with this storm.
Terrain and Travel
- Avoid all avalanche terrain during periods of heavy loading from new snow and wind.
- Avoid exposure to overhead avalanche terrain, avalanches may run surprisingly far.
Problems
Storm Slabs
Snowfall totals may reach 100 cm in parts of the region by Sunday afternoon. The snow (and rain at lower elevations) is falling with very strong southwest wind, forming touchy slabs. The avalanche cycle is expected to continue into Sunday, creating very dangerous avalanche conditions.
Aspects: All aspects.
Elevations: All elevations.
Likelihood
Expected Size
Persistent Slabs
Three different weak layers may be found in the snowpack, which have become easy to trigger during this storm. Diligence will be required until the snowpack strengthens. Avoidance of avalanche terrain is recommended for Sunday, as large and destructive avalanches may fail on these layers and travel far.
Aspects: All aspects.
Elevations: All elevations.
Likelihood
Expected Size
Valid until: Dec 22nd, 2019 5:00PM
