Forecast snow and wind will continue to develop storm slabs. Strong winds may transport loose snow into deep pockets of wind slab.
Confidence
Moderate - Timing, track, or intensity of incoming weather system is uncertain
Weather Forecast
Light westerly winds and increasing cloud overnight with freezing levels at valley bottoms. Flurries or light snow combined with strong southerly winds on Saturday. Alpine temperatures rising slightly on Saturday to about -5. Continued strong southerly winds and light snow on Sunday. Skies clearing on Monday with light winds and no precipitation forecast. Alpine temperatures around -5.
Avalanche Summary
A natural avalanche cycle up to size 2.0 from various aspects was reported on Friday from west of Valemount. We had a report from Valemount on Thursday that in most areas the recent storm snow was mostly unconsolidated, and not reacting as a slab yet. In some areas the storm snow has been pressed into a slab by the winds and is very easy to trigger where it is sitting on a widespread layer of surface hoar. Expect soft storm slabs to continue to be triggered by human activity. We also had a report on Thursday from the Wells Grey area of a skier remotely triggering a size 2.0 slide that was 35 cm deep from 20 metres away. This avalanche was 80 metres wide and released on buried surface hoar in the alpine. This group also reported numerous whumpfs during the day. These reports suggest that there is some variability across the region. I suspect that the south and west of the region may have more storm snow, and the storm snow may have settled into a more cohesive slab in those areas.
Snowpack Summary
The recent storm snow total is now 10-30 cm. that is sitting on buried surface hoar and near surface facets. Some operations reported a thin freezing drizzle crust on the snow surface before the Wednesday morning snow arrived. Storm slabs and isolated wind slabs overlie old surfaces including surface hoar, facets, and possible sun crusts on steep southerly aspects. Below this, the upper pack is mostly drying out (through faceting). In general, the mid and lower snowpack are strong, with any weak layers considered dormant for now. Snowpack depths are variable and shallow snowpack areas may have weak facetted crystals near the ground.
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.