Avalanche Forecast
Issued: Dec 20th, 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 will continue to drop snow and blow strong wind. A natural avalanche cycle is likely underway and very dangerous avalanche conditions will continue into Saturday. Travel in avalanche terrain is not recommended.
Summary
Confidence
High -
Weather Forecast
FRIDAY NIGHT: Cloudy with heavy snowfall, accumulation 20 to 40 cm, strong to extreme southwest wind, alpine temperature -2 C, freezing level 1700 m.
SATURDAY: Cloudy with snowfall, accumulation 20 to 40 cm, strong to extreme southwest wind, alpine temperature -3 C, freezing level 1500 m.
SUNDAY: Cloudy with snowfall, accumulation 5 to 10 cm, light to moderate south wind, alpine temperature -5 C, freezing level 1000 m.
MONDAY: Cloudy with snowfall, accumulation 5 to 10 cm, light to moderate southwest wind, alpine temperature -5 C, freezing level 700 m.
Avalanche Summary
Many large persistent slab avalanches were triggered naturally and by explosives on Friday. This trend is expected to continue into the weekend during the storm.
Snowpack Summary
The storm will continue to hammer the region with about 20 cm of snowfall every 12 hours until Sunday morning. This snow will load multiple weak layers, including:
- a feathery surface hoar layer buried around 50 to 80 cm beneath the new snow.
- a surface hoar layer buried about 70 to 100 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
Around 20 cm of snow is expected to accumulate every 12 hours until Sunday morning, falling with very strong southwest wind. The avalanche cycle is expected to continue on Saturday, 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 Saturday, 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 21st, 2019 5:00PM
