Regions
Northwest Inland.
Snow, wind, and rising freezing levels will increase the avalanche danger. Deeply buried persistent weak layers may be triggered by the increased load from the storm. Patience and a conservative approach to terrain are recommended.
Confidence
Moderate - Timing, track, or intensity of incoming weather system is uncertain
Weather Forecast
Moderate southerly winds with a couple of cm of new snow overnight. Light snow and strong southwest winds on Thursday as the freezing level climbs above the valley bottoms. 5-10 cm of new snow by Friday morning combined with strong southerly winds and freezing levels around 1000 metres. Another 3-5 cm of snow during the day Friday with strong southwest winds and freezing levels dropping down to 500 metres by late afternoon. Moderate southwest winds with broken skies on Saturday as a ridge builds behind the storm.
Avalanche Summary
Some loose dry avalanches up to size 1.0 were reported from the Hankin area on Tuesday in the alpine on steep east aspects. Reports from Monday include extensive natural loose dry sluffing up to Size 1.5 in steep terrain, and one relatively harmless stubborn skier controlled wind slab avalanche in a heavily wind-loaded pocket at the top of a terrain break. On Saturday, there was one report of an intentionally skier triggered size 2 slab avalanche in the Ashman area. This slide may have released on the buried mid-Jan surface hoar layer, down around 50 cm in this area. There was also a report of a size 2.5 slab that was remotely triggered from the far SW corner of the region on Sunday. This slide initiated on the mid-Jan layer and likely stepped down to the Boxing Day surface hoar layer.
Snowpack Summary
Generally 5-20 cm of new snow has accumulated this week. At higher elevations this snow may be covering previously wind affected snow or settled old snow. Below 1200-1400 m the new snow probably sits on a crust. Fresh soft wind slabs are likely in exposed lee terrain. The early or mid January surface hoar layer is reported throughout the region and is generally 30-50 cm deep. Observers have found this persistent weakness on all aspects and at all elevations. It consistently produces moderate "pops" results in snowpack tests. Below this, the Boxing Day surface hoar problem may also be lurking. The mid and lower snowpack is generally quite weak and faceted, especially in lower snowpack areas.
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.