Regions
Kootenay Boundary.
Recent heavy snowfall has over-loaded weak layers, and very large avalanches are still a concern. Conservative terrain selection remains critical.
Confidence
Fair - Timing or intensity of solar radiation is uncertain on Tuesday
Weather Forecast
Remnant moisture from the pineapple express will bring light precipitation to the region on Tuesday morning. By the end of the day, a warm dry ridge of high pressure will develop bringing progressively warmer temperatures and clearing throughout the forecast period. Tuesday: Light snowfall and overcast skies / Light northwest winds / Freezing levels at 1800m Wednesday: Mix of sun and cloud / Moderate southwest winds / Freezing level at 1800m Thursday: Mix of sun and cloud / Moderate southwest winds / Freezing level climbing to 2700m
Avalanche Summary
Over the last few days there was a widespread avalanche cycle to size 3.5. Most of the avalanches were storm slabs which formed in response to new snow and wind, although many avalanches stepped down to the late and mid January surface hoar/crust layers. On Sunday, many of these avalanches were still failing naturally or with remote triggers. Looking forward, very large persistent slab avalanches remain a concern, especially with forecast warm temperatures and potential for solar radiation.At lower elevations where the snowpack is rain-soaked, there is potential for ongoing loose wet or wet slab avalanches. Although if snow surfaces refreeze and form a strong crust, this will be unlikely.
Snowpack Summary
Heavy precipitation over the past few days has resulted in deep and dense storm slabs above about 1800m. At lower elevations heavy rain has saturated the snowpack which, depending on the temperature, will now appear wet or refrozen. Moderate to strong southwest winds have shifted the new snow accumulations into much deeper deposits in exposed lee terrain. Below the recent storm snow you'll find a hard melt freeze crust which exists up to 100cm below the surface. This crust, which formed at the end of January, may have weak overlying surface hoar and is still reported to be very reactive in some areas. Deeper in the snowpack the mid-January surface hoar remains a concern. It can be found down 80-140 cm across the region. In some locations it has reportedly gained quite a bit of strength, but elsewhere it is still producing very large avalanches under the weight of the recent snow load.The mid-December surface hoar layer is now 100 to 170cm below the surface and has become unlikely to fail.
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.