Slab avalanches in steep terrain are still likely following the recent large storm, especially in wind-affected terrain. Conservative terrain choices are recommended.
Confidence
Moderate - Wind speed and direction is uncertain
Weather Forecast
SATURDAY: Flurries with accumulations of 5-15 cm, light to moderate northwest winds, alpine temperatures around -12.SUNDAY: A mix of sun and cloud, light northeast winds, alpine temperatures around -16.MONDAY: Sunny with cloudy periods, light northeast winds, alpine temperatures around -20.
Avalanche Summary
Widespread storm slab activity was reported on Friday including natural and explosive triggered avalanches typically in the size 2-2.5 range.Expect storm slab activity to continue into the weekend and be extra touchy in wind affected terrain. Triggering persistent slab avalanches remains possible in thin snowpack areas in the northern and eastern parts of the region.
Snowpack Summary
Between 50 and 100 cm of new low density snow has fallen over the past week, with the greatest accumulations in the Monashees. Shifting winds with moderate speeds are forming touchy storm slabs in exposed high elevation terrain. The mid-December interface can be found buried 80-120 cm deep and consists of faceted (sugary) crystals and/or surface hoar. Recent tests suggest the the new snow is well bonded to the interface in most areas, but remains a concern in thin snowpack areas such as the eastern and northern parts of the region. The lower snowpack is well consolidated and features a thick rain crust 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.
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.