Avalanche Forecast
Issued: Dec 2nd, 2020 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.
kdevine,
Avalanche Canada
Forecast freezing levels and warm alpine temperatures are uncertain for the North Rockies. Carefully monitor conditions and be extra cautious if you see temperatures above zero, as warm temperatures could result in large avalanches that may catch you by surprise.
Summary
Confidence
Low - Uncertainty is due to the limited number of field observations. Uncertainty is due to difficult to forecast freezing levels.
Weather Forecast
High winds and a strong temperature inversion causing unseasonably warm temperatures up high will dominate the weather pattern for a few days.
WEDNESDAY NIGHT - Clear / southwest wind, 40-60 km/h / alpine low temperature near +3
THURSDAY - Sunny with cloudy periods / southwest wind, 40-60 km/h / alpine high temperature near +4 and cooling in the afternoon
FRIDAY - A mix of sun and cloud with isolated flurries / southwest wind, 50-70 km/h / alpine high temperature near 0 / freezing level 2000 m
SATURDAY - Sunny with cloudy periods / southwest wind, 60-80 km/h / alpine high temperature near +5Â Â
Avalanche Summary
There has been a report of an avalanche fatality near Pine Pass on Saturday, November 28. Reports indicate a size 3 deep persistent slab avalanche at approximately 1600 m elevation on a northeast aspect. The avalanche was approximately 55 cm deep, 800 m wide and ran 400 m in length. The avalanche may have run on a weak layer of faceted crystals sitting on a crust that was buried in early November.
On Tuesday, there were reports of a few explosives triggered wind slab avalanches, size 1-2.5.
If you get out into the mountains, please consider sharing your observations on the Mountain Information Network.
Snowpack Summary
The North Rockies have seen between 30-70 cm of recent storm snow in the past week. Strong southwest winds have likely created widespread wind slabs in the alpine and open areas at treeline. In some areas, the windward slopes have been stripped of the recent snow. Fresh wind slabs may be reactive to human triggers.
A crust that was buried in early November is near the base of the snowpack. In some areas, weak, sugary facets are sitting on this crust. This layer is of most concern on steep terrain in thinner snowpack areas.
Snow depths are approximately 150 cm in the northwest of the region (Pine Pass), 180 cm in the south (Renshaw, Kakwa) and 100 cm in the the northeast (Tumbler ridge). Â
Terrain and Travel
- Watch for newly formed and reactive wind slabs as you transition into wind affected terrain.
- Be aware of the potential for large avalanches due to the presence of a deep persistent slab.
- Avoid steep convexities or areas with a thin, rocky, or variable snowpack.
- If triggered, wind slabs avalanches may step down to deeper layers resulting in larger avalanches.
Problems
Wind Slabs
30-70 cm of snow fell late last week with the highest amounts in the south. Strong southwest winds have built deep wind slabs at treeline and alpine elevations on lee and crossloaded slopes.
Aspects: North, North East, East, North West.
Elevations: Alpine, Treeline.
Likelihood
Expected Size
Deep Persistent Slabs
There is currently 90-120 cm of snow sitting on top of weak a layer of sugary facets that developed above a firm crust which formed in early November. Warm temperatures at upper elevations late Tuesday and through Wednesday may increase the likelihood triggering deep persistent slabs.
Aspects: All aspects.
Elevations: Alpine, Treeline.
Likelihood
Expected Size
Valid until: Dec 4th, 2020 4:00PM
