Avalanche Forecast
Regions: Banff, Banff Yoho Kootenay, East Side 93N, Field, Kootenay, LLSA, Lake Louise, Sunshine, West Side 93N.
5-45 cm of new snow fell with strong SW winds as a cold front passed through Monday. Monitor recent snowfall amounts carefully. Moderate terrain choices with limited overhead hazard are recomended until the storm snow settles and bonds.
Confidence
Moderate
Avalanche Summary
Areas around Yoho and Lake Louise got 30-45 cm of new snow and saw natural avlanche activity out of steep terrain up to size 2 in the storm snow, as well as ski cutting and explosive results at the ski hill. Other areas of the forecast area got significantly less snow and only saw a few small wind slabs in steep lee loaded terrain in the alpine.
Snowpack Summary
5-45+cm of snow arrived Monday with strong SW winds. The storm snow sits over buried sun crusts that are present to ridge crests, and faceted layers on shady aspects. Multiple buried crusts are present in the top 50-70 cm on solar aspects. The basal depth hoar is present at the bottom of the snowpack and remains facetted and weak. Lower elevations have a temperature crust on all aspects.
Weather Summary
Winds will decrease as they switch from moderate SW to light SE on Tuesday. Freezing levels will drop to valley bottom with alpine lows reaching -15°C Monday night, and rising to 1800 m on Tuesday afternoon with alpine temperatures near freezing. No significant precip is expected Tuesday but some convective showers may occur further east.
Terrain and Travel Advice
- Watch for newly formed and reactive wind slabs as you transition into wind affected terrain.
- Continue to make conservative terrain choices while the storm snow settles and stabilizes.
- In areas where deep persistent slabs may exist, avoid shallow or variable depth snowpacks and unsupported terrain features.
Avalanche Problems
Storm Slabs
Areas with 15+ cm of fresh snow will have a storm slab problem. The new snow may fail naturally and will be reactive to human triggering especially over buried sun crusts. Lee areas with newly formed wind slabs and fresh cornices are also a concern.
Aspects: All aspects.
Elevations: Alpine, Treeline.
Likelihood: Likely
Expected Size: 1 - 2
Deep Persistent Slabs
The weak basal facets, as well as mid-pack facets and crusts, remain a significant concern. Many large avalanches on these layers during a recent avalanche cycle indicate that this problem will continue to be a concern until the end of the season.
Aspects: All aspects.
Elevations: Alpine, Treeline.
Likelihood: Possible
Expected Size: 2 - 3.5