Regions
Northwest Inland.
Stormy weather could eventually tip the scales and initiate a natural avalanche cycle that may involve buried weak layers. Conservative terrain selection and avoiding overhead hazards is recommended.
Confidence
Low - Due to the number of field observations
Weather Forecast
SUNDAY: The Arctic front delivers another 10-15 cm of snow with moderate southeast wind, potential for an inversion with alpine high temperatures around -8 C.MONDAY: A break from the storm with isolated flurries, moderate west wind, alpine high temperatures around -6 C.TUESDAY: Another storm brings 15-25 cm with strong to extreme southwest wind and freezing levels climb to roughly 1500 m.
Avalanche Summary
Reports have been limited. At the start of the storm on Wednesday and Thursday skiers triggered a few small slabs on steep convex rolls.There are no recent reports of persistent slab avalanche activity, but some notable large avalanches occurred 5-8 days ago. This includes some large (size 2-3) natural persistent slab avalanches in the Howsons, and two large (size 2.5) remotely triggered avalanches north of Kispiox. We have no information from the Smithers area, but suspect a similar deeper weakness could exist there too. Activity on buried weak layers is most suspect during periods of heavy loading or rapid warming, hence it's time to be cautious.
Snowpack Summary
Fresh snow will continue to accumulate the next few days. 30-50 cm has already accumulated since Thursday. The snow has mostly fallen as low density powder, but may have settled in some areas that experience a brief period of warming on Friday. Westerly winds are likely blowing snow around in exposed terrain and forming touchy slabs.40-70 cm of snow lies over a crust and/or weak feathery surface hoar layer buried in mid-January. The crust exists well into the alpine and the surface hoar can be found in sheltered areas in the lower alpine and treeline elevations. Another two crust / surface hoar layers that formed in December are buried 60-90 cm below the surface. These layers produced sudden results in recent snowpack tests and have been the suspected weak layer in recent large remotely (from a distance) triggered avalanches.
Problems
Storm Slabs
Storm Slab avalanches are the release of a cohesive layer (a slab) of new snow that breaks within new snow or on the old snow surface. Storm-slabs typically last between a few hours and few days (following snowfall). Storm-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.