Natural avalanches possible, human triggered probable.
Treeline
Natural avalanches unlikely, human triggered possible.
Below Treeline
Natural avalanches unlikely.
Alpine
Natural avalanches possible, human triggered probable.
Treeline
Natural avalanches possible, human triggered probable.
Below Treeline
Natural avalanches unlikely.
Alpine
Natural avalanches possible, human triggered probable.
Treeline
Natural avalanches possible, human triggered probable.
Below Treeline
Natural avalanches unlikely.
Regions
Banff Yoho Kootenay.
The snowpack has almost reached tipping point with 40cm of soft snow overlying the Dec. 15 weak layer (surface hoar & facets). Warming temperatures and wind this weekend could push it over the edge at treeline and above.
Weather Forecast
A warmup is expected starting Saturday with alpine temps in the -3 to 5C range on the Eastern end of the range. Increasing Westerly winds will accompany this and we could see alpine elevation gusts in the 50-80kmh range by the evening with a couple cm of snow. It looks warm through the coming weekend.
Snowpack Summary
30cm snow has fallen over the past week with limited wind effect except near ridge crests. There is now a total of 30-50 cm overlying the Dec.15 persistent weak layer of facets and some surface hoar which is becoming reactive at treeline and above. This layer is producing easy to moderate sudden collapse results. Click for an example from today.
Avalanche Summary
A solo backcountry skier triggered a size 2 avalanche on Richardson's Ridge yesterday outside the Lake Louise Ski Resort boundary - this was a treeline area with a shallow snowpack. As well, numerous small windslabs were observed to have run over the past 48 hours and there has been plenty of settlements being reported at treeline and above.
Confidence
Problems
Persistent Slabs
Persistent Slab avalanches are the release of a cohesive layer of snow (a slab) in the middle to upper snowpack, when the bond to an underlying persistent weak layer breaks. Persistent layers include: surface hoar, depth hoar, near-surface facets, or faceted snow. Persistent weak layers can continue to produce avalanches for days, weeks or even months, making them especially dangerous and tricky. As additional snow and wind events build a thicker slab on top of the persistent weak layer, this avalanche problem may develop into a Deep Persistent Slab.
Wind Slabs
Wind Slab avalanches are the release of a cohesive layer of snow (a slab) formed by the wind. Wind typically transports snow from the upwind sides of terrain features and deposits snow on the downwind side. Wind slabs are often smooth and rounded and sometimes sound hollow, and can range from soft to hard. Wind slabs that form over a persistent weak layer (surface hoar, depth hoar, or near-surface facets) may be termed Persistent Slabs or may develop into Persistent Slabs.