Steady snowfall and strong winds will test the generally weak and shallow snowpack over the next 72hours. Be vigilant of changing conditions, especially new windslabs in cross loaded terrain.
Weather Forecast
Steady increase in snowfall towards the weekend, with weather models predicting between 15-30cm. Temperatures to remain fairly seasonal, ranging from -8C to -20C at treeline. Strong, gusty Westerly winds expected throughout the storm.
Snowpack Summary
Variable 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 generally faceted and weak, and is beginning to slide naturally in lee terrain and steep Westerly aspects.
Avalanche Summary
Several new size 2 windslabs out of N to NE terrain around ridgelines (~2100m). These slides ran an impressive 300m, were 50m wide on average, but the sliding layer is unknown due to visibility. Numerous healthy avalanches up to size 2.5 were also observed on steep, Westerly terrain between 2500-2800m. These ran 400m, were 60m wide and 50cm thick.
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.