Winds will play a large role in driving the avalanche danger on Wednesday as there's lots of loose snow available for redistribution. Use extra caution if the snow feels stiff or slabby.
Confidence
Moderate - Due to the number of field observations
Weather Forecast
Wednesday: Light flurries / Strong westerly winds / Alpine temperatures of about -13Thursday: About 10cm of new snow / Strong southerly winds / Alpine temperatures of about -10Friday: Light flurries / Moderate westerly winds / Alpine temperatures of about -12
Avalanche Summary
No new avalanches were reported at the time of publishing this bulletin. I'm sure there was some natural wind slab activity in response to new snow and wind on Monday night. Continued strong ridgetop winds should promote ongoing wind slab activity. For the short term, I also expect loose dry avalanches to be triggered easily in steep sheltered terrain.
Snowpack Summary
By Tuesday morning, up to 35 cm of new low density snow had fallen. In higher elevation terrain where the winds were stronger, I would expect new wind slab formation on lee and cross-loaded features. 60-90 cm below the surface you'll find the mid-December interface which consists of a variety of old snow surfaces including wind affected snow, faceted (sugary) crystals, and/or surface hoar crystals. Recent tests suggest the the new snow is well bonded to the interface in some areas. However, a few public and professional reports suggest this layer may be reactive in some areas and worth investigating before pushing into steeper terrain. The thick mid-November crust layer typically sits 1-2 m down in the snowpack. Recent test results on this layer suggest it is generally well bonded to the adjacent snow with the possible exception of shallow snowpack areas. This layer is considered dormant at this time but remains an isolated concern that we will likely be tracking through much of the season.
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.
Loose Dry
Loose Dry avalanches are the release of dry unconsolidated snow and typically occur within layers of soft snow near the surface of the snowpack. These avalanches start at a point and entrain snow as they move downhill, forming a fan-shaped avalanche. Other names for loose-dry avalanches include point-release avalanches or sluffs.