Avalanche Forecast
Regions: Banff, Banff Yoho Kootenay, East Side 93N, Field, Kootenay, LLSA, Lake Louise, Little Yoho, Sunshine, West Side 93N.
Mt. Stephen will be closed on Tuesday, Dec 27 for avalanche control - no climbing or skiing there. Strong SW winds, warm temperatures and 20-30 cm of recent snow have combined to make dangerous avalanche conditions with widespread, new windslabs bonding poorly to the underlying snowpack. Seek out sheltered locations to find the best quality and most stable snow.
Confidence
Moderate
Avalanche Summary
Not many observations today due to the poor visibility, but several size 1.5 windslab avalanches were reported by ski hill avalanche control teams and observed on the fans above Crowfoot Trees.
Of note to ice climbers, Bourgeau left-hand went sz 2.5 within the last 48-hours.
Snowpack Summary
Strong to extreme westerly winds at upper elevations have blown 20-30 cm of recent HST into widespread, windslabs susceptible to human triggering. This problem sits atop a layer of facets and surface hoar buried on Dec 17, but any avalanche of note that starts may step down to the deeper persistent layers near the ground. Cooling temperatures later this week should provide a minor improvement.
Weather Summary
The active weather continues on Tuesday with another 5-10 cm expected. The strong winds will taper through the day on Tuesday and overnight into Wednesday with some cooling temperatures by mid-week. More stable weather is expected later this week (Thurs/Fri).
Terrain and Travel Advice
- If triggered, wind slabs avalanches may step down to deeper layers resulting in larger avalanches.
- Uncertainty is best managed through conservative terrain choices at this time.
Avalanche Problems
Wind Slabs
Widespread fresh windslabs exist at treeline and above throughout the region. These slabs overlie weak, faceted snow that was on the surface during the prolonged deep freeze and human triggering is likely in many locations. Sheltered locations provide the best snow.
Aspects: All aspects.
Elevations: Alpine, Treeline.
Likelihood: Very Likely
Expected Size: 1.5 - 2.5
Deep Persistent Slabs
The whole snowpack is thin, weak and faceted, meaning that any avalanche starting in the upper layers could easily release on the ground. Avoid large alpine open slopes >30 degrees, especially where shallow and windswept and don't linger any longer than neccessary under overhead hazard.
Aspects: All aspects.
Elevations: Alpine, Treeline.
Likelihood: Likely
Expected Size: 1 - 3
Loose Dry
The snowpack below treeline is comprised almost entirely of weak, unconsolidated facets that sluff easily in very steep terrain. Steep gullies or chutes below treeline could develop larger than-expected sluffs, running further and with more force than usual.
Aspects: All aspects.
Elevations: Treeline, Below Treeline.
Likelihood: Possible - Likely
Expected Size: 1 - 1.5