Avalanche Forecast
Issued: Dec 18th, 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.
kdevine,
Avalanche Canada
Wind slabs are likely to be encountered at upper elevations and may be reactive to human triggering, especially in lee features.
Summary
Confidence
Weather Forecast
FRIDAY NIGHT - Mainly cloudy with flurries, 5 cm / southwest wind, 50-80 km/h, gusting to 110 km/h / alpine low temperature near -4 / freezing level 1300 m
SATURDAY - A mix of sun and cloud with scattered flurries / southwest wind, 40-80 km/h / alpine high temperature near -3 / freezing level 1500 m
SUNDAY - A mix of sun and cloud / southwest wind, 30-60 km/h / alpine high temperature near 0 / freezing level 2000 m
MONDAY - A mix of sun and cloud with isolated flurries / southwest wind, 30-40 km/h gusting to 75 km/h / alpine high temperature near 0 / freezing level 2000 m
Avalanche Summary
There were a few reports of both natural and explosives triggered avalanches up to size 2 on Thursday and Friday.
Please consider sharing your observations on the Mountain Information Network. Thank you to those that have already submitted this winter!
Snowpack Summary
Up to 20 cm of recent new snow and strong to extreme southwest wind have likely formed reactive wind slabs at treeline and in the alpine.
This recent snow means there is now 30-50 cm above the early December crust which exists up to approximately 2000 m. Use caution if you find cohesive snow above this crust; there may be weak faceted grains above or below the crust.
The base of the snowpack consists of a hard melt-freeze crust from early-November that may have faceted grains around it. There has not been recent avalanche activity on this layer but it remains on our radar. The most likely spot to trigger it would be on thin and rocky slopes.
Snowpack depths vary substantially in the region with the average snowpack depth at treeline being approximately 100 cm.
Terrain and Travel
- Watch for newly formed and reactive wind slabs as you transition into wind affected terrain.
- If triggered, wind slabs avalanches may step down to deeper layers resulting in larger avalanches.
- Avoid areas where the snow feels stiff and/or slabby.
Problems
Wind Slabs
Strong southwest wind is forecast for the rest of the weekend along with rising temperatures. Use caution near ridges and avoid leeward slopes, particularly where you find stiff wind affected snow.
Aspects: North, North East, East, South East, North West.
Elevations: Alpine, Treeline.
Likelihood
Expected Size
Persistent Slabs
30-50 cm of snow currently sits above a buried crust from early December. Sugary, facets above and/or below the crust may weaken the bond and the persistent slab may become reactive, especially to human triggers.
Aspects: All aspects.
Elevations: All elevations.
Likelihood
Expected Size
Valid until: Dec 19th, 2020 4:00PM
