Fresh, touchy wind slabs and cornices have developed in the alpine. Light loads or brief periods of intense sun may have enough energy to trigger them.
Weather Forecast
A mainly cloudy day with light SW winds. Freezing levels will remain at valley bottom. Wednesday will bring scattered flurries, freezing levels rising to 1200m, and light winds.
Snowpack Summary
Between 50 and 100cm of storm snow now overlies the Nov 13th Crust. Previous strong winds from the Southerly quarter have created wind slabs and cornices. Wind slabs could be hiding under more recently fallen snow. A temp/sun crust is buried around 30cm deep on solar aspects, but it is spotty in distribution.
Avalanche Summary
Reports of small, size 1 skier-triggered soft slabs from E-NE aspects in the Balu Pass area yesterday. Also in the backcountry, small loose, dry avalanches in steep terrain were noted running fast and far at tree-line. Over the weekend, there were numerous avalanches, size 2 to 3, from steep N-facing terrain on Mt Macdonald and Cheops.
Confidence
Due to the number of field observations
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.