Strong southwest winds have loaded leeward terrain and gully features. Natural avalanches observed up to size 2.5 in the Alpine.Hard wind slab or a shallow weak snowpack exists Tree Line and above. Soft snow found in sheltered areas Below Tree Line.
Weather Forecast
Steady increase in snowfall towards the weekend, with weather models predicting between 15-20cm. Temperatures to remain fairly seasonal, ranging from -8C to -20C at treeline. Strong, gusty Westerly winds expected throughout the storm.
Snowpack Summary
Strong SW winds have built slabs in lee features and cross loaded gullies. Weak layers include; buried surface hoar (Dec 11) in sheltered NE aspects around treeline and the Nov 12 crust approximately 30cm from the ground. The snowpack is faceted and weak.
Avalanche Summary
Recent avalanche activity up to Sz 2 on N-NE-E terrain below ridgeline, ~2400m running 300m and 50m wide on average. Also saw numerous Sz 2.5 on westerly terrain in steep, rocky, cross loaded terrain between 2400-2700m, 50cm deep, 50-80m wide and running up to 400m.
Confidence
Intensity of incoming weather systems is uncertain
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.