Avalanche Forecast
Regions: Banff, Banff Yoho Kootenay, East Side 93N, Field, Kootenay, LLSA, Lake Louise, Sunshine, West Side 93N.
Use caution at high elevations, particularly where the snowpack (and the February 3 crust) is thin.
Watch for increasing winds and rising alpine temperatures Saturday that may have the potential to to increase slab development and sensitivity.
Confidence
Moderate
Avalanche Summary
A size 2 and 2.5 skier-triggered deep persistent slab in the Cirque Forepeak area occurred Tuesday showing that the deeper layers can still be triggered in thin snowpack areas and at high elevations.
Further to the west, skiers triggered a size 2.5 slab at 3050m on Mt Vaux Thursday while boot-packing. Luckily there were no injuries. Again: use caution at higher elevations.
Snowpack Summary
10- 20 cm of snow sits over the Feb 3 crust found in most locations (except above 2500m on north aspects). At low elevations, this crust is a sign of the stabilization that occurred during the warming event. Where it is thin: consider the snowpack to be largely as it was before the warming. Persistent weak layers remain present in the mid and bottom of the snowpack and have recently produced avalanches on the ground in thin areas at high elevations (ie where the Feb 3 crust is thin).
Weather Summary
A ridge of high pressure persists over the region through Saturday. Clear skies will bring cold nights (TL temps -20C) and a cool day. Watch for moderate south winds to bring rising temperatures likely setting up a temperature inversion.
As winds shift west, clouds will invade on Sunday bringing a chance of flurries. Temperatures will rise slightly with TL overnight lows near -10C.
Terrain and Travel Advice
- Avalanche hazard may have improved, but be mindful that deep instabilities are still present.
- Be especially cautious near rock outcroppings, on steep convexities and anywhere the snowpack feels thinner than average.
- Watch for wind-loaded pockets especially around ridgecrest and in extreme terrain.
Avalanche Problems
Wind Slabs
Winds have been light, but wind effect and slab development have been noted at the upper elevations. NE winds were observed to be transporting snow at peak level Thursday. Expect winds to increase to mod as they shift to the south Saturday and a temperature inversion to increase slab sensitivity.
Aspects: All aspects.
Elevations: Alpine.
Likelihood: Possible
Expected Size: 1 - 2
Deep Persistent Slabs
We are using this problem to represent 3 weak layers: two separate persistent layers in the top 50 cm and the basal weakness.
Sporadic avalanche activity continues on these layers and the theme seems to be steep, thin snowpack areas in the high alpine.
Aspects: All aspects.
Elevations: Alpine.
Likelihood: Unlikely - Possible
Expected Size: 1.5 - 3