Avalanche Forecast
Issued: Dec 19th, 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
A powerful storm will impact the region Thursday night and into the weekend. Substantial snowfall and strong wind will create very dangerous avalanche conditions. Travel in avalanche terrain is not recommended until the snowpack stabilizes.
Summary
Confidence
Moderate - Forecast snowfall amounts are uncertain.
Weather Forecast
THURSDAY NIGHT: Cloudy with heavy snowfall, accumulation 20 to 30 cm, strong to extreme southwest wind, alpine temperature -3 C, freezing level 1000 m rising to 1700 m.
FRIDAY: Cloudy with heavy snowfall, accumulation 30 to 50 cm, strong to extreme southwest wind, alpine temperature -2 C, freezing level 1700 m.
SATURDAY: Cloudy with snowfall, accumulation 40 to 50 cm, strong to extreme southwest wind, alpine temperature -2 C, freezing level 1700 m.
SUNDAY: Cloudy with snowfall, accumulation 5 to 10 cm, light to moderate south wind, alpine temperature -5 C, freezing level 1000 m.
Avalanche Summary
A few small avalanches were triggered on Wednesday by skiers. Avalanche activity will likely increase Thursday night into Friday. A natural avalanche cycle is likely to occur during this storm.
Snowpack Summary
Around 50 to 80 cm of snow may accumulate Thursday night into Friday. 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 become very likely to trigger given the substantial amount of new snow and strong wind forecast with this storm.
Problems
Storm Slabs
A natural avalanche cycle is likely to occur during this storm that will drop snowfall between Thursday night and Sunday. The timing of the avalanche cycle is uncertain, but it is prudent to expect that it will occur at any point. Human-triggered avalanches are very likely to occur on Friday. Give this new snow some time to bond to underlying layers.
Aspects: All aspects.
Elevations: All elevations.
Likelihood
Expected Size
Persistent Slabs
Three different weak layers may be found in the snowpack, which may become easy to trigger with the new snowfall. Diligence will be required until the snowpack strengthens. Avoidance of avalanche terrain is recommended for Friday, as large and destructive avalanches may fail on this layer.
Aspects: All aspects.
Elevations: All elevations.
Likelihood
Expected Size
Valid until: Dec 20th, 2019 5:00PM
