Regions
Northwest Coastal.
Stormy weather will elevate the danger this weekend. Minimize your exposure to avalanche terrain when there's rapid loading from new snow and wind.
Confidence
Moderate - Intensity of incoming weather systems is uncertain
Weather Forecast
FRIDAY: Snow with 10-20 cm Thursday night and another 10-20 cm on Friday / moderate southwest wind increasing to strong in the afternoon / alpine temperatures around -3 C.SATURDAY: Another 10-30 cm of snow / strong west wind / alpine temperatures around -3 C.SUNDAY: Another 10-30 cm of snow / strong west wind / alpine temperatures around -5 C.
Avalanche Summary
Evidence of natural activity from Tuesday's storm was observed on Wednesday. Avalanches included small to large storm slabs (size 1-2) and dry loose avalanches in steep terrain. In inland areas east of Terrace, a few natural avalanches released on the mid-January crust as well.A few size 1-2 persistent slab avalanches were also triggered by skiers on Wednesday, all of which failed on the mid-January crust which was roughly 60 cm deep. These occurred in the more inland areas east of Terrace and in northern parts of the region. The avalanches occurred on north alpine slopes and on a southwest treeline slope. The mid-January layer was also active in the Shames area last Saturday, where a skier triggered a size 2 avalanche on a northeast alpine slope. In this case, the weak layer was composed of surface hoar.Overall, activity on persistent weak layers was limited during this last storm, but enough to suggest it may remain reactive through this upcoming stormy period.
Snowpack Summary
Fresh snow will continue to accumulate the next few days. Areas around Terrace have already seen over 60 cm the past few days. Warm temperatures are promoting the settlement of new snow, while westerly winds are blowing snow around in exposed areas and forming touchy slabs.A weak layer buried in mid-January remains a concern and is now 60-100 cm deep. In most areas this layer is a crust, but it may also be surface hoar in sheltered areas at treeline and below. This layer has produced a few human triggered avalanches throughout the region over the past week, and may become more reactive as it adjusts to the weight of the new snow.In thinner snowpack areas (north and inland), deeper crust / surface hoar layers that were buried in December and early January may still be a concern. They are over 100 cm below the surface, but may be triggerable from thin spots.
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.