Avalanche Forecast
Regions: Banff, Banff Yoho Kootenay, East Side 93N, Field, Kootenay, LLSA, Lake Louise, Sunshine, West Side 93N.
The snowpack is slowly adjusting, but human triggering remains a risk. The strong to extreme wind and warm temperatures forecast for Thursday will add to the slab development.
Confidence
Moderate
Avalanche Summary
On Thursday, helicopter avalanche control on Mt. Field, Stephen, and Dennis produced slab avalanches up to size 3. Any spot that looked like it could avalanche, did. Many avalanches triggered slabs from the side walls of the path.
On Wednesday, a skier triggered a size 1.5 avalanche in Lipalian 3, just outside the Lake Louise ski area boundary. One skier was carried 60 m but remained on the surface, uninjured. Sunshine patrol triggered a size 2 deep slab with explosives.
Snowpack Summary
10-30 cm of storm snow has fallen with mild temps and recent strong S-SW winds helping to form wind and persistent slabs. This snow sits over a layer of weak facets, surface hoar or sun crust from the cold snap.
The mid-pack is generally weak facets, while depth hoar and crusts form an even weaker base. The snowpack is the weakest in eastern areas where snow depths are low. In these areas, the basal weaknesses should be carefully considered.
Weather Summary
For Thursday - Friday, flurries with showers at lower elevations are forecast. Freezing levels are 1900 m on Thursday and 2200 m on Friday. Only trace accumulations are expected in the region. Winds will be strong to extreme on Thursday from the west.
Terrain and Travel Advice
- In areas where deep persistent slabs may exist, avoid shallow or variable depth snowpacks and slopes above cliffs.
Avalanche Problems
Persistent Slabs
10-30 cm of storm snow and strong S-SW winds have loaded lee areas at treeline and above with slabs up to 60 cm deep. The slab sits on a weak layer of facets, surface hoar or sun crust. Human triggering will remain likely in steep or wind loaded terrain for the next few days.
Aspects: All aspects.
Elevations: Alpine, Treeline.
Likelihood: Possible - Likely
Expected Size: 1 - 2
Deep Persistent Slabs
The recent storm has added load to an already shallow and weak snowpack. With this additional weight and warmer temperatures, there may be a reawakening of this problem in isolated areas. Areas of concern include thin, shallow, and rocky slopes.
Aspects: All aspects.
Elevations: Alpine, Treeline.
Likelihood: Unlikely
Expected Size: 1.5 - 2.5