Avalanche Forecast
Issued: Dec 9th, 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.
wlewis,
Avalanche Canada
The best riding will be found in sheltered terrain. Keep your head up in wind loaded features near ridgeline - expect reactivity where slabs sit over a crust.
Avoid shallow rocky start zones, deeper weak layers are still a concern.
Summary
Confidence
Moderate - Uncertainty is due to the speed, direction, or duration of the wind and its effect on the snowpack. We have a good understanding of the snowpack structure and confidence in the weather forecast
Weather Forecast
A front pushes through the interior on Saturday bringing warmer weather, moderate to heavy snowfall and very strong ridgeline winds.
THURSDAY NIGHT: Cloudy with a chance of flurries, moderate westerlies. Freezing levels at valley bottom.
FRIDAY: Trace amounts of snow, most cloudy. Freezing level at valley bottom, alpine highs of -9. Light westerlies.Â
Snow begins overnight, bringing up to 5cm by morning.Â
SATURDAY: 5-15cm over the day. Freezing levels climb to 1500m. Alpine highs of -3. Strong to extreme southwest winds.Â
SUNDAY: Light snow continues Saturday night (3-10cm), and tapers throughout the day Sunday (2-5cm). Winds decrease to moderate southwesterlies. Freezing levels below 1000m. Alpine highs of -6.Â
Avalanche Summary
Yesterday, natural and skier triggered slab avalanches were observed at treeline and above to size 1.5.
Explosive control work near Golden on Dec 5th produced a size 2 slab avalanche that failed to ground in a steep and unsupported terrain feature. A naturally triggered size 3 was also observed on a west facing slope in the Northern zone of the Purcells, believed to have occurred around the 2nd of December.Â
Two Mountain Information Network (MIN) reports (MIN 1 and MIN 2) from Dec 3 in Quartz Creek also reported deep persistent avalanches failing at the base of the snowpack.Â
While these observations are almost a week old, this deeply buried weak layer is still a concern.
Snowpack Summary
Up to 50cm of storm snow sits over a thick and supportive melt freeze crust on all aspects up to 2400m. Westerly winds have redistributed new snow into deeper deposits in wind loaded features at higher elevations.
A late October facet/crust layer of concern sits at the bottom of the snowpack above 1900m. This layer has been reactive to human triggers, producing large avalanches. This layer is widespread and will likely continue to be a layer of concern.
Average snowpack depth at treeline is 100-180cm, with the deepest snowpack found near the Bugaboos.Â
Terrain and Travel
- Watch for newly formed and reactive wind slabs as you transition into wind affected terrain.
- Be aware of highly variable recent wind loading patterns.
- Be mindful that deep instabilities are still present and have produced recent large avalanches.
Problems
Wind Slabs
Strong winds and fresh snow has built wind slabs in lee features in the alpine and treeline. Approach ridge crest and crossloaded features lower on slopes with caution, variable winds have created unusual loading in some areas.
Aspects: North, North East, East, South East, South, South West, North West.
Elevations: Alpine, Treeline.
Likelihood
Expected Size
Deep Persistent Slabs
A widespread weak layer of facets and depth hoar exists at the base of the snowpack above 1900m.
Avoid thin and rocky start zones where this layer may sit closer to the surface, and big open slopes capable of producing large avalanches.
Aspects: All aspects.
Elevations: Alpine, Treeline.
Likelihood
Expected Size
Valid until: Dec 10th, 2021 4:00PM
