Regions
Banff Yoho Kootenay.
While the alpine snowpack structure does not inspire too much confidence, we have been through a good test. With long periods of above freezing temperatures near mountain top and many people out exploring, no avalanche activity has been reported.
Weather Forecast
The high pressure system remains entrenched over the Rockies until at least Friday. The temperature inversion will rebuild Monday with mountain-top freezing levels through midday Tuesday. Moderate winds can be expected at upper elevations and lower in areas that funnel West winds.
Snowpack Summary
Extensive wind effect at treeline and above. Sun crusts are present on some steep south facing slopes. Surface hoar up to 25mm has formed below 2200m and surface faceting is in progress. 15-40 cm of snow lies over the Nov 27th and Nov 23rd crusts. Both of these now overlie the Halloween crust/facet layer that sits 30-50cm above the ground.
Avalanche Summary
During the last few days with inverted temperatures yielding above freezing conditions treeline and above, only a few very small loose wet avalanches in the alpine were observed. These were in steep rocky terrain that was in the sun, and sheltered from the wind. Where observed, these did not triggered any deeper weaknesses.
Confidence
Due to the number of field observations
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.