Regions
Banff Yoho Kootenay.
While only occasional natural activity has been observed, open areas still hold the potential for larger releases of slab over the weak facets. The overall structure is poor and any steep terrain should be treated cautiously.
Weather Forecast
Cool temperatures and light flurries are forecast. As of yet things are still forming but we may be looking at a bit of snow and slightly warmer temps reaching us by Sunday night before things dry out and cool down again by Tuesday. Unfortunately, the snowpack is presently weak and cannot support loading.
Snowpack Summary
Winds over the past week have created wind slabs in most alpine areas. 20-30 cm of facetting recent snow and wind slab sits over top of the weak December facet layer which in turn sits on the Nov 12 rain crust. This poor snow structure of firm snow over weak facets will likely be with us for some time and is not something to put much confidence in.
Avalanche Summary
On a flight from Banff to the Bow Peak area Saturday, a number of recent natural slab avalanches up to size 2 on all aspects above treeline were observed. These slabs failed on the weak mid pack facets and several of them within the last couple days. Two small loose dry avalanches were noted in Kootenay on Friday from steep rocky terrain.
Confidence
Timing, track, or intensity of incoming weather system is uncertain on Monday
Problems
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.
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.