Recently formed wind slabs have been slow to gain strength and remain a concern.
Confidence
Moderate - Forecast snowfall amounts are uncertain on Saturday
Weather Forecast
THURSDAY: Cloudy with sunny periods and lingering flurries, light southerly winds, -8 at 1500m. FRIDAY Isolated flurries or rain at lower elevations, moderate southerly winds, freezing level rising to 1500m. SATURDAY snow starting overnight with up to 5cm by morning, flurries continuing through the day, light to moderate westerlies, freezing levels remain at 1500m.
Avalanche Summary
Isolated natural and skier controlled slab avalanches up to size 2 continue to be reported from across the region. There is also the ongoing possibility of triggering more destructive persistent slab avalanches in isolated open, unsupported terrain features at and below treeline.
Snowpack Summary
Up to 40cm of snow has fallen in the last week and remains mostly unaffected by wind. The new snow may be sitting on a crust that extends up to 1900m. The surface hoar layer from early January is now typically down 80-120cm in most places. Although the layer has become harder to human trigger and is variably reactive in snowpack tests, it still has the potential for wide propagations. I would continue to show respect for this layer in steep, open terrain at treeline and below. In general, the lower snowpack below this layer is well settled and strong.
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.