NW winds have redistributed snow from recent storms, building slabs in a slightly unusual pattern. Now almost 1m of snow at higher elevations on top of weak December layer of facets and in places surface hoar but still willows showing below 1800m.
Weather Forecast
Clear but continued NW winds until Saturday morning when another cold front arrives. Temperatures will drop again and we could see 10-15cm of snow at higher elevations. Winds will switch back to the normal SW following the passage of the front.
Snowpack Summary
The slab over the persistent weak layer consisting of surface hoar and facets over a strong crust is now 80 to 100cm thick at up ridgetop but only 40cm below treeline. Strong west and northwest winds have create slabs, some in slightly unusual locations because of the northerly component of the winds.
Avalanche Summary
The new snow is hiding any evidence of recent avalanche activity however at least three large avalanches occurred during the last storm. Natural avalanche activity seems to have tapper off for no but could increase with new snow forecast for Sunday.
Confidence
Intensity of incoming weather systems is uncertain on Sunday
Problems
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.
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.