Regions
Northwest Inland.
Watch for areas where wind and storm snow have formed cohesive slabs above the recently buried crust/ surface hoar layer. Triggering of deeper snowpack layers is also possible from thin snowpack areas or, a step-down from a surface release.
Confidence
Moderate - Intensity of incoming weather systems is uncertain
Weather Forecast
TONIGHT: Mostly cloudy. Ridge wind light, southeast. Temperature -12. Freezing level valley bottom.SATURDAY: Mix of sun and cloud. Ridge wind light to moderate, east. Temperature -12. Freezing level valley bottom.SUNDAY: Cloudy, flurries. Accumulation 5-10 cm. Ridge wind strong, southeast. Temperature -12. Freezing level valley bottom. Alpine inversion.MONDAY: Cloudy, flurries. Accumulation up to 5 cm. Ridge wind moderate, southwest. Temperature -12. Freezing level valley bottom.
Avalanche Summary
Thursday there was a report of skiers, north of Kispiox, remotely triggering a Size 2-2.5 avalanche from a safe location on a ridge that released on the adjacent slope on a northwest aspect at 1650 m. A weak layer buried late-December was the suspected failure plane.Wednesday there was a report of a skier-triggered Size 1 wind slab avalanche on a northwesterly aspect at 1650 m in the northern part of the region, east of Ningunsaw.Tuesday there were reports of easily-triggered wind slabs 30-40 cm deep releasing to Size 1 in wind-loaded areas near ridge crests in the alpine in the southern part of the region.On Monday there were reports from areas north of Kispiox of reactive storm slabs up to size 1.5 and 25 cm deep releasing with skier traffic on steeper, convex terrain.Reports from late last week showed a notable increase in persistent slab activity at lower elevations in the Howson Range. In this area, three Size 2 releases failed on steeper terrain with remote triggers on the mid-December weak layer, found 50 cm below the surface.
Snowpack Summary
Recent light snowfalls have gradually brought 20-60 cm of new snow across the region. This new snow has buried the mid-January interface which features a crust that exists well into the alpine and isolated pockets of surface hoar in sheltered areas at lower alpine and treeline elevations. Below the mid-January interface, deeper weak layers in the snowpack include crusts and surface hoar layers that were buried late-December and mid-December and now lie 50-80 cm below the surface. Recent persistent slab activity over a surface hoar and facet 'combo' buried in at low elevations in December suggests that a persistent slab problem may be developing as the mid and upper snowpack consolidate into a stiffer slab over this layer.
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.