Avalanche Forecast
Regions: Banff Yoho Kootenay.
Explosive avalanche control is planned for Thursday March 5 on Mt. Bourgeau (above the Sunshine Village Road), Mt. Whymper and Mt. Simpson (Highway 93 South). Respect the closure signs and do not enter these areas.
Weather Forecast
Mainly cloudy on Thursday with another 5-10cm of snow, temp range of -16 to -4 and consistently strong SW winds. Thursday night into Friday will see another 10cm and gradually decreasing winds. Another 10cm forecasted for Saturday with cooling temps and light winds.
Snowpack Summary
30-40 cm of storm snow in the past few days brings the weekly total to ~60cm. Strong to extreme Westerly winds continue to form storm/wind slab at all elevations. Watch for buried sun crust on steep solar aspects. In thin snow pack areas a dense mid-pack sits over a weak, faceted base. Thick snowpack areas have a denser base with few weaknesses.
Avalanche Summary
Several natural storm slab avalanches up to sz 2.5 observed along highway 93S today where intense wind loading was occurring.
With continued strong to extreme winds and incoming snow in the forecast over the next few days, expect natural avalanche activity to increase.
Confidence
Timing, track, or intensity of incoming weather system is uncertain on Thursday
Avalanche Problems
Storm Slabs
Expect to find slab formation on lee aspects and open areas from the alpine to below tree line. Loose dry sluffing from steep terrain is also a concern, especially in gulleys, terrain traps and above cliffs.
- Steep unsupported terrain and slope convexities are the likely locations to awaken the storm slab.
- Watch for fresh storm slabs on exposed lee slopes and open areas at all elevations.
Aspects: All aspects.
Elevations: All elevations.
Likelihood: Likely - Very Likely
Expected Size: 1 - 2.5
Deep Persistent Slabs
Avalanche activity on the basal facets has slowed down but the weakness in the snowpack remains a concern. These are hard to predict, but are most likely in areas with a thin snowpack (<130cm) where the basal facets and depth hoar are prominent.
- Use caution in thin snowpack areas.
- Pay attention to overhead hazards like cornices which could easily trigger the deep persistent slab.
Aspects: All aspects.
Elevations: Alpine, Treeline.
Likelihood: Unlikely - Possible
Expected Size: 2 - 3.5