Strong winds and new snow has increased avalanche hazard, especially above treeline. Avoid heavily loaded features and traveling near or below recently formed cornices.
Weather Forecast
We are mid-storm with an additional 8cm of accumulation expected today. Strong southerly winds with gusts to 70km/h and freezing levels rising to 1800m this afternoon. We return to a weak westerly flow later tonight with unsettled conditions and trace amounts of precipitation through to Tuesday. A high pressure ridge builds next week.
Snowpack Summary
Strong winds and new snow created a wind slab instability on lee features and in avalanche start zones. The Nov 23 temperature crust is down 15-30cm below treeline and snow is bonding poorly to this layer. The Nov 13 crust is widespread and down 70-120cm. Warmer temps this afternoon will encourage slab development in the upper snowpack.
Avalanche Summary
A report of a close call in Cheops N #6 (Nicci's Notch Couloir) in the Connaught drainage where a size 2.0 avalanche terminated 50m from a group of 2. Skiers also reported skier controlled size 1.5 slabs failing on the the Nov 23 temperature crust on open slopes below treeline. Several natural size 2.0-2.5 were observed in the highway corridor.
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.