Avalanche Forecast
Issued: Dec 4th, 2021 4:00PM
The alpine rating is , the treeline rating is , and the below treeline rating is Known problems include Wind Slabs and Deep Persistent Slabs.
zryan,
Avalanche Canada
Stiff wind slabs formed by cold temperatures should be approached with caution. Although wind slabs may be stubborn to trigger, they do have the potential to step down to deeper layers.
Summary
Confidence
Moderate - Uncertainty is due to the limited number of field observations. Uncertainty is due to the fact that deep persistent slabs are particularly difficult to forecast.
Weather Forecast
Saturday Overnight: Partially cloudy with alpine temperatures reaching -30 C overnight. Light northwest winds shift west in the early morning and increase to strong at ridgetop.Â
Sunday: Increasing cloud throughout the day with up to 2 cm of new snow accumulation. Moderate to strong westerly winds. Alpine temperatures rise to -22 C.Â
Monday: An incoming frontal system will bring a cloudy day with strong southwest winds. Up to 10 cm of new snow throughout the day, heaviest in the afternoon. Temperatures rise to -10 C by the afternoon.
Tuesday: A cloudy day with continuous snowfall. Up to 30 cm of accumulation may occur by the end of Tuesday night accompanied by strong southwest winds. Alpine temperatures around -10 C.Â
Avalanche Summary
Lots of whumping and cracking have been reported across the region, which is most likely associated with an early-season shallow snowpack, wind slabs, and a weak facet/crust layer at the base of the snowpack.
On Tuesday, a size 2.5 skier-remote persistent slab was reported on the MIN (see report here). The avalanche was triggered from around 100m away, by a group of 5 riders on an east aspect at 1400m. The avalanche was suspected to have failed on an early-season facet/crust layer. Â
Snowpack Summary
Varied wind directions in the past week will create a mix of old and new wind slabs on all aspects of the alpine and treeline. Expect these wind slabs to be quite stiff from the drop in temperatures on Saturday.Â
Snow depth at treeline is approximately 80-120 cm, depths in the alpine range from 100-160 cm.
A facet/crust layer can be found near the bottom of the snowpack. This layer has been reported as being reactive to human triggering in the past week, with a notable skier-remote avalanche on Tuesday.
Terrain and Travel
- If triggered, wind slabs avalanches may step down to deeper layers resulting in larger avalanches.
- Avoid thin areas like rock outcroppings where you're most likely to trigger avalanches failing on deep weak layers.
- Back off if you encounter whumpfing, hollow sounds, or shooting cracks.
Problems
Wind Slabs
Varied winds over the past week will have created wind slabs on all aspects of the alpine and treeline. Cold temperatures over the past few days will likely stiffen these slabs. This will decrease the likelihood of human triggering, but keep in mind that if triggered wind slabs can step down to the late October crust, creating larger avalanches.
Aspects: All aspects.
Elevations: Alpine, Treeline.
Likelihood
Expected Size
Deep Persistent Slabs
A late October facet/crust layer near the base of the snowpack has shown reactivity in the past week. There is very little information about this layer, and as a result, careful snowpack evaluation will be necessary to manage it.
Aspects: All aspects.
Elevations: Alpine, Treeline.
Likelihood
Expected Size
Valid until: Dec 5th, 2021 4:00PM
