Regions
Northwest Coastal.
Continued wind, snow and warming will add more stress to buried weak crystals. Very large avalanches have been running from the alpine to valley bottom. Conservative terrain selection remains critical.
Confidence
Fair - Due to the number of field observations
Weather Forecast
The active weather pattern will continue as a fairly strong and moist southwest flow remains aimed at the region. Monday: Light to moderate snowfall, intensifying throughout the day / Light southwest winds intensifying to strong values throughout the day / Freezing level at 1200m Monday night and Tuesday: Up to 30cm of snow / Strong southwest winds / Freezing level at 1200m Wednesday: Light to moderate snowfall / Strong southwest winds / Freezing level at 1000m
Avalanche Summary
Recent observations have been somewhat limited, likely because of inclement weather. That said, storm slab avalanches to size 2.5 were noted in the north of the region on Saturday. With forecast weather, large storm slab avalanche activity is expected to continue with the potential to step-down to highly destructive persistent weaknesses. At lower elevations where precipitation is falling as rain, wet slab and loose wet avalanches remain a concern.
Snowpack Summary
Continued heavy snowfall (with rain below approximately 1500-1000 m) and extreme southwest winds have built fresh deep and dense storm slabs. A rain crust and/or surface hoar layer buried mid-January is down around a metre. Recent reports mention that this weakness has become reactive with recent heavy loading and has been responsible for much of the recent large avalanche activity. The November crust near the bottom of the snowpack is generally well bonded, but may 'wake up' with intense loading this week. There is potential for isolated very large and deep avalanches.
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.
Loose Wet
Loose Wet avalanches are the release of wet unconsolidated snow or slush. These avalanches typically occur within layers of wet snow near the surface of the snowpack, but they may quickly gouge into lower snowpack layers. Like Loose Dry Avalanches, they start at a point and entrain snow as they move downhill, forming a fan-shaped avalanche. Other names for loose-wet avalanches include point-release avalanches or sluffs. Loose Wet avalanches can trigger slab avalanches that break into deeper snow layers.