Watch for signs of reverse loading as the wind switches directions. Recent loading has also potentially awakened persistent weak layers, so conservative terrain selection remains critical.
Confidence
High - The weather pattern is stable
Weather Forecast
SUNDAY: A mix of sun and cloud, 20-40 km/h northeast winds, alpine temperatures around -16.MONDAY: Sunny with cloudy periods, 10-20 km/h east winds, alpine temperatures around -20.TUESDAY: Sunny with cloudy periods, 20-30 km/h east winds, alpine temperatures around -13.
Avalanche Summary
Widespread storm slab activity was reported on Friday including natural and explosive triggered avalanches typically in the size 2-2.5 range, with some larger avalanches in extreme terrain. A few cases of storm slabs stepping down to the mid-December interface were reported on steep south-facing slopes and on wind-loaded features. A fatal avalanche occurred in the Clemina area of the North Monashees. The avalanche was triggered by a rider on a wind-loaded feature, and potentially released on the mid-December interface. On Sunday, expect the recent storm snow to be most reactive in wind exposed terrain where moderate winds are forming fresh storm slabs. 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. There remains to be some uncertainty on the distribution and reactivity of this layer. Some recent patterns suggest the layer may be more reactive on steep south facing slopes and in areas with thinner snowpacks 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
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.