Avalanche Forecast
Issued: Dec 17th, 2021 4:00PM
The alpine rating is , the treeline rating is , and the below treeline rating is Known problems include Wind Slabs and Persistent Slabs.
zryan,
Avalanche Canada
Wind will be the main driver of danger today. Seek out wind sheltered terrain where you can avoid wind slabs and find great riding.
Summary
Confidence
Weather Forecast
Friday Overnight: Increasing cloud cover into the evening with winds strengthening strong to extreme from the southwest. Temperatures rising steadily reaching -10 C in the alpine by early morning.
Saturday: A mainly cloudy day with flurries, 2-10 cm of accumulation. Strong to extreme southwest winds, freezing levels rising to around 500m in the afternoon. Continued snowfall overnight with another 5-10 cm of accumulation.
Sunday: Partially cloudy with light flurries, trace accumulation. Wind decreasing into the moderate range from the southwest in the morning and tapering into the afternoon.
Monday: Mainly clear, cloud cover increasing with isolated flurries in the afternoon. Moderate southwest winds at ridgetop and alpine temperatures around -10 C.
Avalanche Summary
On Friday, the South Rockies field team was out in the Window mountain area. They observed several natural wind slab avalanches in the alpine up to size 1.5. Read their full report here.
Earlier in the week, operators have reported several large (size 2) explosive-triggered avalanche releasing on the early December crust layer.
Snowpack Summary
Since Monday, up to 30 cm of snow has accumulated, with another 5-10 cm expected through out the day today. Yesterday, new snow was redistributed by northwest winds into wind slabs in the alpine and treeline. Today, we can expect continued wind slab development as southwest winds redistribute the new snow into fresh wind slabs in the alpine and treeline.
Below this new snow, more consolidated snow from the previous weekend storm sits over a substantial crust that formed in early December. This crust is likely 20 cm thick (or more) and is present across aspects below 2400m. A thin layer of weak facets (sugary snow) can found above this crust that has demonstrated reactivity in snowpack tests and avalanche activity.
Snowpack depths vary due to strong to extreme southwest winds from early December that stripped snow off of exposed areas and deposited it onto lee slopes. Below 2300m, several early season crusts are breaking down and forming a cohesive lower snowpack. Snowpack depths range from 60-110 cm at treeline elevations and taper quickly below 1900m.
Terrain and Travel
- Avoid freshly wind loaded terrain features.
- Avoid shallow snowpack areas, rock outcroppings and steep convex terrain where triggering is most likely.
Problems
Wind Slabs
Strong southwest winds will continue to redistribute this week's 30 cm of snow, along with new snow throughout the day, into wind slabs in the alpine and treeline.
Aspects: North, North East, East, South East, South, North West.
Elevations: Alpine, Treeline.
Likelihood
Expected Size
Persistent Slabs
A layer of weak facets (sugary snow) can be found down 40-70 cm over a crust that formed in early December. This layer has recently produced large avalanches from explosive triggers.
Aspects: All aspects.
Elevations: All elevations.
Likelihood
Expected Size
Valid until: Dec 18th, 2021 4:00PM
