Avalanche Forecast
Regions: Banff, Banff Yoho Kootenay, East Side 93N, Field, Kootenay, LLSA, Lake Louise, Little Yoho, Sunshine, West Side 93N.
Heating and wind transport have triggered a few avalanches around the region over the last couple of days. Fresh slabs are evident and cornices are large.
While the winds are forecast to back off tomorrow, this may allow the sun to deliver more significant heating as freezing levels rise beyond what they have been for a while....
Confidence
Moderate
Avalanche Summary
Saturday on a response to the 93N, Visitor Safety observed a size 1.5 slab on the East of Dolomite Peak: up 40cm deep running on a crust (April2?) and a deep slab on the North side of Noseeum Mountain that failed to the ground sz 2 in the past 48-72hrs.
Friday, during a flight along Hwy 93N Fri Visitor Safety observed evidence of a size 2.5 wind slab avalanche stepping down to the Feb 3rd on Bow Peak (NE aspect) and several size 1.5's on similar terrain in the area.
Snowpack Summary
5 to 15 cm of snow in the past two days sits over a recent crust. Up to 50cm of snow sits on more extensive crusts from the start of April that go as high as 2200m on north aspects. Moist snow on steep solar slopes Saturday.
The midpack is generally well settled down to the February 3 persistent weak layer which remains a concern in shallow snowpack areas on northerly alpine aspects. In these areas, no crusts are found in the upper snowpack and the midpack remains thin and weak.
Weather Summary
Saturday night: Clearing. Winds SW 20-30 km/h. Freezing levels return to valley bottom.
Sunday: Winds diminish to light. Freezing levels rise to 2500m. Cloud builds in the afternoon. Partly cloudy overnight. Freezing levels drop to around 1900m overnight winds increase to 20-30km/h.
Monday: Freezing levels rise to 2000m. Increasing cloud in the afternoon with flurries or rain beginning late in the afternoon.
Terrain and Travel Advice
- Watch for wind-loaded pockets especially around ridgecrest and in extreme terrain.
- If triggered, wind slabs avalanches may step down to deeper layers resulting in larger avalanches.
- Avoid thin areas like rock outcroppings where you're most likely to trigger avalanches failing on deep weak layers.
Avalanche Problems
Wind Slabs
20-30 cm of snow over the past 8 days combined with strong south-southwest winds has created widespread wind effect treeline and above. Watch for pockets of new and old slab to be reactive on steep terrain and use additional caution if these slabs sit over buried crusts.
Aspects: All aspects.
Elevations: Alpine, Treeline.
Likelihood: Possible - Likely
Expected Size: 1 - 2.5
Persistent Slabs
The Feb 3 layer is down 60-130 cm. In shallow snowpack areas on northerly alpine aspects, this layer may still be sensitive to skiers, with remote triggering observed in a couple of instances last week. All recent avalanches that initiated on this Feb 3 layer stepped down to the basal facets/ground.
Aspects: North, North East, East, North West.
Elevations: Alpine.
Likelihood: Possible
Expected Size: 2 - 3
Loose Wet
Monitor the impacts of solar radiation as the day develops. Expect moist snow to develop on steep slopes which may become reactive over buried crusts. Anticipate a deterioration in existing surface crusts at lower elevations for the end of your day.
Aspects: East, South East, South, South West, West, North West.
Elevations: All elevations.
Likelihood: Likely
Expected Size: 1 - 2