Avalanche Forecast
Issued: Dec 19th, 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.
jcoulter,
Avalanche Canada
Wind slabs in open areas may still be reactive. More sheltered treeline terrain will likely provide better riding quality.
Summary
Confidence
Weather Forecast
SATURDAY NIGHT - Trace to 5 cm / west wind, 40-80 km/h / alpine low temperature near -9 / freezing level at 1400
SUNDAY - A mix of sun and cloud/ trace to 5 cm / west wind, 40 km-90 km/h / alpine high temperature near -5 / freezing level 1800 m
MONDAY - 8-15 cm / southwest wind, 30-40 km/h gusting to 75 km/h / alpine high temperature near 0 / freezing level 1800 m
TUESDAY - 15-20 cm / northeast wind 15-40 km/h / freezing level 1700m
Avalanche Summary
On Saturday a natural size 2.5 avalanche was spotted out of extreme, shallow, rocky, wind affected terrain in the Crowsnest Pass. It was thin, but propagated widely. The date of the event was uncertain.
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
Recent incremental snowfalls 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
Incremental snowfall amounts, strong westerly wind and rising temperatures are forecast for Sunday. 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 20th, 2020 4:00PM
