Up to 25cm of recent storm snow has fallen, with a further 15+cm still to come. Strong SW winds and warm temps are promoting storm slab development, particularly in the Alpine. Cautious route selection is advised.
Confidence
Fair - Timing, track, or intensity of incoming weather is uncertain
Weather Forecast
Cool Alpine temperatures with winds increasing to 100km/h from the W. Between 15 and 20cm of new snow is expected for the next 24hrs.
Avalanche Summary
Observations were very limited due to poor visibility, but two small to medium size slides were heard (but not seen) coming from a steep E aspect at 2700m.
Snowpack Summary
Up to 10cm of new snow overnight with storm snow totals up to 25cm over the past 48hrs. Storm slab formation is ongoing in the Alpine and selected locations at Treeline due to strong SW winds. Shears exist with the storm snow, failing in the easy range on compression tests. The Nov rain crust, now buried an average of 100cm at Treeline continues to produce hard shear results.
Problems
Storm Slabs
Storm Slab avalanches are the release of a cohesive layer (a slab) of new snow that breaks within new snow or on the old snow surface. Storm-slabs typically last between a few hours and few days (following snowfall). Storm-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.
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.