Regions
Northwest Inland.
Winds continue to dominate the headlines this season! Seek sheltered terrain to avoid wind slabs and find better snow quality.
Confidence
Fair - Timing of incoming weather systems is uncertain
Weather Forecast
Synopsis: A center of low pressure crosses the region on Friday resulting in moderate precipitation – 10-15 cm. The freezing level should be at valley bottom and winds are moderate to strong from the west. The weekend looks mainly cloudy, cooler, and a bit drier. Expect 5 cm each day – maybe a bit more later on Sunday. Temperature should drop by around 8-10 degrees. Ridge winds are light on Saturday rising to moderate from the SW on Sunday.
Avalanche Summary
There is one new report of several small natural avalanches out of steep terrain and one size 2 slab from a steep SE aspect in the Babine Mountains between Dec 29-31. On Dec. 29 a rider triggered a size 1.5 avalanche on a north aspect in the alpine at 1700m in the Sinclair area. The small steep wind loaded slope was triggered when the machine was climbing, the rider reportedly rode out of the avalanche behind the debris. See the Mountain Information Network for a photo and more details.
Snowpack Summary
Strong outflow winds earlier this week left a variety of wind affected conditions in exposed terrain at all elevations. Some windward aspects and ridge lines were scoured down to bare ground. North facing slopes that still have snow are likely wind pressed. The thickest and likely hardest slabs should be found on south facing features and some degree of cross-loading is likely found everywhere else. A layer of buried surface hoar, down 30-50 cm, appears to be spotty in distribution but is still a concern. Near the bottom of the snowpack is a crust facet combo that was formed in mid-November. This layer is currently dormant and produces variable results in snowpack tests. I suspect it will remain sensitive to new inputs in the form of new snow and wind for the foreseeable future.
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.