Avalanche Forecast
Regions: Banff, Banff Yoho Kootenay, East Side 93N, Field, Kootenay, LLSA, Lake Louise, Little Yoho, Sunshine, West Side 93N.
There has been continued natural, explosive and human-triggered avalanches, with many starting or stepping down to the deep persistent layer. Continued inputs of snow and/or wind this weekend will keep the hazard elevated.
Confidence
Moderate
Avalanche Summary
A flight in the Northern part of the park Friday saw continued natural activity over the past 24 hours. Mainly wind slabs with some stepping down to persistent or deep persistent layers. Lake Louise observed a natural size 2.5 on "Speed run", and a natural size 3 in Richardson's bowl. Both initiated on the basal facets. As well, lots of recent explosive triggered and natural avalanches.
A size 2.5 deep persistent natural avalanche at Quartz ridge was triggered by a cornice on Thursday. There was also a MIN report of a skier remote triggering a size 2.5 avalanche in the Healy Creek area on Wednesday from 100m away showing continued reactivity to a skier's weight.
Snowpack Summary
5-20cm over the last 24 hours (average 10cm). New and previous wind slabs have formed from strong winds over the past week. These slabs overlie several persistent weak layers that exist 30-60cm below the surface. These weak layers are a combination of crusts, facets and surface hoar formed and buried in January and are producing sudden test results. Deeper in the snowpack, the November crust/facet layer ~40 cm above the ground also continues to produce sudden test results.
Weather Summary
Saturday: 5cm with decreasing West winds 40-60km/h to NW 20-30km/h in the afternoon. Freezing levels 1300-1500m and alpine temperatures -10C to -15C.
Sunday: Strong winds return as another system arrives with 10-20cm in the forecast. Freezing levels 1600-1800m and alpine temperatures -5C to -10C.
More details can be found in the Mountain Weather Forecast.
Terrain and Travel Advice
- Make conservative terrain choices and avoid overhead hazard.
- If triggered, wind slabs avalanches may step down to deeper layers resulting in larger avalanches.
- Cornice failure may trigger large avalanches.
Avalanche Problems
Persistent Slabs
Slabs 30-60 cm deep overlie three persistent weak layers formed in January which are a mix of crusts (solar aspect), facets (cold aspects) and isolated surface hoar. We have primarily seen avalanches failing on crusts on solar aspects but are watching for activity on other aspects as well.
Aspects: South East, South, South West, West.
Elevations: Alpine, Treeline.
Likelihood: Likely
Expected Size: 1 - 2.5
Deep Persistent Slabs
This problem is at the base of the snowpack and consists of weak facets and depth hoar near an old crust formed in November. The layer is very weak and will not get stronger anytime soon. Thus the upper snowpack sits on an unstable foundation. This problem exists in most locations and requires avoidance or very careful travel through avalanche terrain.
Aspects: All aspects.
Elevations: Alpine, Treeline.
Likelihood: Likely
Expected Size: 1.5 - 3
Wind Slabs
5-20cm of new snow overnight adds to previous wind slabs formed from strong winds over the past week. Use caution in all leeward areas with wind effect. These avalanches have the potential to start small, but then step down to the deeper weak layers.
Aspects: North, North East, East, South East, South.
Elevations: Alpine, Treeline.
Likelihood: Very Likely
Expected Size: 1 - 2