Regions
Northwest Inland.
Be extra cautious around convexities where wind slabs and persistent slabs are easiest to trigger.
Confidence
Moderate - Intensity of incoming weather systems is uncertain on Saturday
Weather Forecast
THURSDAY: Isolated flurries / light to moderate southwest wind / alpine temperatures around -10 C.FRIDAY: Flurries with accumulations of 5-10 cm / moderate west wind / alpine temperatures around -12 C.SATURDAY: Flurries with accumulations of 5-15 cm / moderate west wind / alpine temperatures around -10 C.
Avalanche Summary
On Tuesday, a small storm slab (size 1.5) was triggered by a skier on a southwest aspect at 1250 m. Natural activity was also likely during the storm. Otherwise, most of the recent reported activity has been loose dry snow sluffing in steep terrain. Some persistent slab activity has been reported over the past few days as well. A large naturally-triggered size 3 slab avalanche was reported on an east aspect at 1900 m in the Howsons on Monday, and two large remotely triggered avalanches (size 2.5) were reported late last week on north at west aspects around 1600 m north of Kispiox. The December weak layer was the suspected failure plane.
Snowpack Summary
Strong winds have built wind slabs in exposed terrain. 30-60 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 50-80 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
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.