Regions
Northwest Inland.
New snowfall amounts are uncertain for Thursday night. Pay close attention to how much snow falls in your riding area, and be prepared to back off to conservative terrain.
Confidence
Low - Intensity of incoming weather systems is uncertain on Thursday
Weather Forecast
Weather models are calling for up to 15cm of new snow on Thursday night with another 10cm of new snow on Friday evening. Generally light flurries are forecast for Saturday while a mix of sun and cloud is expected on Sunday. Ridgetop winds on Friday will be strong from the south, becoming light on Saturday and Sunday. Freezing levels will hover around 1200m on Friday and then rise to about 1400m for the weekend.
Avalanche Summary
On Wednesday, a size 3 deep persistent slab avalanche was accidentally triggered by a skier in alpine terrain in the north of the region. To our knowledge, nobody was injured in the incident. The slab, which ran on basal facets, was up to 200cm deep, 200m wide and 500m long. There have been a handful of recent similar avalanches triggered on basal facets in the mountains north of Kispiox. Although observations have been limited, I suspect new snow and wind on Wednesday night also promoted a round of wind slab activity at treeline and in the alpine.
Snowpack Summary
On Wednesday night 5-15cm of new snow fell. Much of this new snow was likely shifted by strong winds into new wind slabs in exposed lee terrain. A layer of surface hoar from early January can be found in isolated locations between 60 and 140cm down. There hasn't been any activity reported on this layer for a couple of weeks now and it is becoming less of a concern. The snowpack in shallower areas sits on a weak base layer of facetted snow. Recently, this layer has been active in the north of the region, responsible for several large avalanches in unsupported alpine terrain.
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.
Deep Persistent Slabs
Deep Persistent Slab avalanches are the release of a thick cohesive layer of hard snow (a slab), when the bond breaks between the slab and an underlying persistent weak layer deep in the snowpack. The most common persistent weak layers involved in deep, persistent slabs are depth hoar or facets surrounding a deeply buried crust. Deep Persistent Slabs are typically hard to trigger, are very destructive and dangerous due to the large mass of snow involved, and can persist for months once developed. They are often triggered from areas where the snow is shallow and weak, and are particularly difficult to forecast for and manage.