Avalanche Forecast
Regions: Banff, Banff Yoho Kootenay, East Side 93N, Field, Kootenay, LLSA, Lake Louise, Sunshine, West Side 93N.
Change is coming as a notable period of calm weather comes to an end.
Be aware of increasing winds on Tuesday: these winds are expected to increase natural avalanche activity in the region.
Confidence
Moderate
Avalanche Summary
A field team on a flight with perfect visibility throughout Banff, Yoho and Kootenay observed a few natural size 2 windslabs in lee alpine terrain and a cornice failure that ran further than expected.
Snowpack Summary
10-20cm of low-density snow overlies a weak, faceted, mid and lower snowpack. This surface snow will be transported easily by incoming winds, so expect slab development as the winds pick up on Tuesday. At the bottom of the snowpack, weak depth hoar and facets associated with old crusts are found. An average of 60-100cm of snow can be found at treeline elevations.
Weather Summary
The story of the next few days is wind. After a period of very calm conditions, the winds are forecasted to increase throughout the day on Tuesday. Expect strong to extreme ridgetop winds overnight on Tuesday and Wednesday. Temperatures will remain cold (-5 to -15 at treeline) and minimal to no snow accumulation by Friday.
Terrain and Travel Advice
- Avoid thin areas like rocky outcrops where you're most likely to trigger avalanches on deep weak layers.
- Pay attention to the wind; once it starts to blow, sensitive wind slabs are likely to form.
- Be careful with sluffing in steep terrain, especially above cliffs and terrain traps.
Avalanche Problems
Wind Slabs
Forecasted winds on Tuesday will blow the 10-20 cm of loose dry snow on the surface and create sluffing and windslab conditions. We expect avalanche activity to increase as the winds increase throughout the day.
Aspects: North, North East, East, South East, South.
Elevations: Alpine, Treeline.
Likelihood: Possible
Expected Size: 1 - 2
Loose Dry
The surface snow will sluff easily in steep alpine terrain as the winds pick up on Tuesday
Aspects: All aspects.
Elevations: Alpine.
Likelihood: Likely
Expected Size: 1 - 1.5
Deep Persistent Slabs
Weak facets and depth hoar near the base of the snowpack are associated with old crusts. While the faceting process is weakening existing upper and mid-pack slabs, continue to be very cautious anywhere there is stiffer snow overlying this basal weakness.
Aspects: All aspects.
Elevations: Alpine, Treeline.
Likelihood: Possible
Expected Size: 1.5 - 3