Avalanche Forecast
Regions: Banff, Banff Yoho Kootenay, East Side 93N, Field, Kootenay, LLSA, Lake Louise, Little Yoho, Sunshine, West Side 93N.
After two days of very warm weather, we'll transition back to a winter-like weather pattern as temps cool and snow arrives late in the day.
A solid refreeze is not certain Sunday night. Carefully assess slopes that haven't seen a solid recovery from the warmth.
Windslabs have surprised folks of late, so monitor slopes for wind effect.
Confidence
Moderate
Avalanche Summary
There have been numerous reports of avalanches stepping down to the Feb. 3/basal facet layer over the past several days. (See photos) Largely triggered by strong solar radiation.
There have also been widespread reports of smaller, but more numerous windslabs (East/north aspects of the alpine) and wet loose (solar slopes in the alpine).
Snowpack Summary
Steep northerly aspects above 2000 m still hold dry snow. Wind slabs/wind effect will be found in all aspects of the alpine and north aspects of treeline, while all solar aspects at treeline and below will have a significant crust.
The midpack is 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
Sunday eve.: No precip forecast, alpine low 0 °C, wind out of the west, 15-35 km/h.
Freezing level @ 2000 meters.
Mon: A mix of sun and cloud, with no precipitation forecast, alpine high -1 °C. Ridgetop winds are expected to be out of the west, 20-30 km/h.
Freezing level @ 2200 meters.
Tues: Up to 9 cm of snow, more to the east. Alpine High -8 °C, ridge winds north: 20 km/h gusting to 45 km/h.
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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 have created widespread wind effect in the alpine. 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: North, North East, East, West, North West.
Elevations: Alpine, Treeline.
Likelihood: Possible - Likely
Expected Size: 1 - 2
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