Although the trend shows improvement the potential for triggering an avalanche is greatest at higher elevations due to recent heavy snowfall and strong winds.
Weather Forecast
A ridge of high pressure will build over BC resulting in much drier and cooler weather for the next few days. Most areas should see a mix of sun and cloud with slight chance of the odd flurry. Freezing levels should gradually drop to 500 m on Saturday and to valley bottom for Sunday and Monday. Winds ease off and become light and variable.
Avalanche Summary
A widespread natural avalanche cycle with slides up to size 3.5 was reported south of Valemount on Thursday. Large slab avalanches were observed above 2000 m and numerous wet slides were observed at lower elevations in steep terrain. Similar activity was likely in other parts of the region. Natural avalanche activity should taper off heading into the weekend as temperatures cool and conditions dry out; however, it could still be possible to trigger fresh wind slabs or storm slabs at higher elevations where most of the recent precip has been snow.
Snowpack Summary
The snow surface was moist or wet below 2000 m and moist up to around 2400 m. Cooler temperature on Friday may have created a surface crust, possibly with a bit of fresh snow on top. At higher elevations (above 1800 m) there is 30-70 cm of dense storm snow sitting on a sun crust or surface hoar. In exposed alpine areas this new snow has been blasted around by strong southerly winds. Reports from the region suggest that anywhere from 50-150 cm of settling snow overlies one or more weak layers which formed during November. Snowpack tests suggest that these weak layers are getting harder to trigger but still have the potential to produce large avalanches if triggered. Recent wind has likely created deep and dense wind slabs in lee features in exposed alpine terrain.
Problems
Storm Slabs
Storm Slab avalanches are the release of a cohesive layer (a slab) of new snow that breaks within new snow or on the old snow surface. Storm-slabs typically last between a few hours and few days (following snowfall). Storm-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.