Avalanche Forecast
Issued: Dec 24th, 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.
MBender,
Avalanche Canada
The load sitting on a variety of buried weak layers has reached a tipping point. If triggered, avalanches running on these weak layers will likely be large and destructive. Continue to choose conservative terrain in the coming days.
Summary
Confidence
Weather Forecast
THURSDAY NIGHT: Clear periods, light southwest wind, alpine temperature near -12 C.
FRIDAY: Mix of sun and cloud, light southwest wind, alpine temperature near -7 C.
SATURDAY: Scattered flurries, light west wind, alpine temperature near -7 C.
SUNDAY: Mainly cloudy with sunny breaks, light west wind, alpine temperature near -8 C.
Avalanche Summary
On Wednesday there was a report of a snowmobile triggered size 2 deep persistent slab avalanche in the north of the region. This MIN post highlights the avalanche and the current nature of the snowpack.
On Tuesday there were several reports of deep persistent slab avalanches running size 2-3 on southeast, east and northeast aspects. Three of these were size 2's triggered by skiers. Check out this MIN report from Tuesday afternoon for an example. As well, there were numerous size 1-1.5 explosives controlled storm slab avalanches.
During the day on Monday reports indicate a few explosives controlled size 1-2 storm slab avalanches in the north of the region.
Snowpack Summary
30 to 75 cm of storm snow fell last week. Winds blowing from a variety of directions have built slabs in lee features at upper elevations, reactive cornices have grown too.
Below the storm snow, there are a variety of layers of concern. The early December surface hoar is down 30 to 80 cm below the surface now. It recently been sensitive to remote triggering which is well illustrated in this MIN post from the Golden area.
Below, or near the surface hoar you may encounter a crust. This crust can be bound as high as 2400 m in the south of the region and 1800 m in the north.
The lower snowpack is characterized by more crusts, the most notable is a rain crust from early November that is 50 to 130 cm deep. This crust is sitting near the base of the snowpack, surrounded by a weak layer of sugary facets. It is most likely to be reactive to human triggers or in a step-down from a smaller avalanche in shallow, rocky areas.
Terrain and Travel
- Uncertainty is best managed through conservative terrain choices at this time.
- Be aware of the potential for large avalanches due to the presence of buried surface hoar.
- If triggered, wind slabs avalanches may step down to deeper layers resulting in larger avalanches.
- Remote triggering is a concern, watch out for adjacent and overhead slopes.
- Avoid shallow, rocky areas where the snowpack transitions from thick to thin.
Problems
Wind Slabs
Wind switching directions has created wind slabs on a variety of aspects.
Aspects: All aspects.
Elevations: Alpine, Treeline.
Likelihood
Expected Size
Persistent Slabs
A slab rests on a persistent weak layer which has the capacity to propagate avalanches across terrain features. A weak layer of surface hoar buried in the middle of the snowpack as well as a crust near the base of the snowpack are both a concern for human triggering.
Aspects: All aspects.
Elevations: All elevations.
Likelihood
Expected Size
Valid until: Dec 25th, 2020 4:00PM
