Regions
Northwest Inland.
A persistent slab above a crust will take time to stabilize. Wind slabs are also lurking in the alpine: Evaluate the terrain and snowpack carefully before committing to steeper terrain.
Confidence
Moderate - Timing, track, or intensity of incoming weather system is uncertain
Weather Forecast
We're looking at a series of small systems impacting the region throughout the forecast period. The winter weather train keeps rolling into town! MONDAY: Snow in the afternoon (5cm). Strong south wind, freezing level around 1200 m with alpine temperatures around -3 C.TUESDAY: 5-10 cm Monday overnight into Tuesday afternoon, strong southwest wind, freezing levels 1300m.WEDNESDAY: Lingering flurries (5cm possible) moderate south wind, freezing levels 1200m, alpine temperatures around -4 C.
Avalanche Summary
On Saturday, several wind slabs to Size 1.5 were reported on (east) northeast aspects in the north of the region. On Friday, loose snow avalanches were reported at treeline in steep terrain in the south of the region. Reports from Wednesday are limited to several Size 1 loose wet avalanches running on a sun crust at lower elevations. On Tuesday, a skier near Hazelton remotely triggered a Size 1 avalanche that subsequently triggered two other Size 2 avalanches on a persistent weak layer (30 cm deep). The avalanches occurred on northeast aspects at 1400 m.Last Monday, a Size 3 slab avalanche was triggered by a cornice fall on a north aspect at 1700 m north of Kispiox. The cooling weather should help stabilize the persistent slab, but human triggering is still possible in steep or unsupported terrain.
Snowpack Summary
Variable and unsettled weather has given 5-15cm of new snow in the past few days. Winds have been moderate southerly, and sufficient to transport snow in exposed terrain. Recent warming and sun have likely left a crust on solar aspects and below 1300 m (reportedly breakable crust below 1000m). Snow from the past week or so has settled into a 20-60 cm thick slab above an older crust interface. Reports suggest the bond to the crust is poor and has resulted in a reactive slab, in addition to weaknesses down 30-35cm within the storm snow itself (giving sudden planar results in snowpack tests). Weak sugary snow near the ground has been a dormant instability, but it may still be possible to trigger in steep rocky terrain.
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.