Avalanche Forecast
Issued: Dec 11th, 2021 4:00PM
The alpine rating is , the treeline rating is , and the below treeline rating is Known problems include Storm Slabs.
ahanna,
Avalanche Canada
Storm slabs will remain most reactive where wind continues to load deep deposits onto leeward slopes. An upside-down configuration over a weak layer in the upper snowpack means that reactivity may persist for longer than usual after the storm.
Summary
Confidence
Moderate - A small change in the upper snowpack could dramatically change avalanche conditions.
Weather Forecast
Saturday night: 5-10 cm of new snow. Strong to extreme southwest wind. Treeline temperatures around -1 C. Freezing level 1400 m.
Sunday: 5-10 cm of new snow. Strong southwest wind easing through the day. Treeline temperatures around -6 C. Freezing level 1000 m.
Monday: 5-10 cm of new snow. Moderate southeast wind. Treeline temperatures around -4 C. Freezing level 1000 m.
Tuesday: A mix of sun and cloud. Light wind. Treeline temperatures around -8 C. Freezing level 500 m.
Avalanche Summary
We are still awaiting observations of avalanche activity during the storm. Skier control work near Nelson produced storm slabs up to size 1.5 and explosive control work in Kootenay Pass produced storm slabs up to size 2.5. These avalanches were 30-50 cm deep, failing on the thick crust layer described in the snowpack summary.
Snowpack Summary
Ongoing snowfall and wind will continue to load leeward terrain features at upper elevations Sunday. An upside down upper snowpack has resulted from 15-30 cm of warm snow falling over unconsolidated low density snow sitting on a thick crust. This crust, now 40-70 cm deep, is well detailed in this MIN report from before the storm. Snow depths are roughly 80-140 cm at treeline.
Terrain and Travel
- Fresh snow rests on a problematic persistent slab, don't let good riding lure you into complacency.
- Continue to make conservative terrain choices while the storm snow settles and stabilizes.
- Avoid freshly wind loaded terrain features.
- Watch for signs of instability like whumpfing, hollow sounds, shooting cracks or recent avalanches.
Problems
Storm Slabs
Storm slabs will be most reactive where deeper deposits have been wind loaded into lee aspects. Avoid these areas until they have a chance to stabilize. Recent snow rests on a weak layer which means that reactivity may persist for longer than usual after the storm.
Aspects: North, North East, East, South East.
Elevations: All elevations.
Likelihood
Expected Size
Valid until: Dec 12th, 2021 4:00PM
