Regions
Kootenay Boundary.
The snowpack will need time to adjust to the heavy load of the new snow, and rain saturation at lower elevations. Very large avalanches are still a concern. Conservative terrain selection remains critical.
Confidence
Fair - Intensity of incoming weather systems is uncertain on Monday
Weather Forecast
The pineapple express will bring continued precipitation until Monday. On Tuesday and Wednesday a warm dry ridge of high pressure will develop. Monday: Up to 15cm of snow at higher elevations / Strong southwest winds / Freezing level at 1800m Tuesday: Mix of sun and cloud / Light northwest winds / Freezing level at 1800m Wednesday: Mix of sun and cloud / Light West winds / Freezing level at 1800m
Avalanche Summary
Over the last few days there was a widespread natural avalanche cycle to size 3. Most of the avalanches were storm slabs which formed in response to new snow and wind. At lower elevations, a couple of wet slabs to size 3 were observed. With forecast weather storm slab avalanches will remain a concern with the potential to step down to deeper persistent layers. Loose wet and wet slab avalanches will also remain likely.
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. Moderate to strong southwest winds have shifted the new snow accumulations into much deeper deposits in exposed lee terrain. Weaknesses are expected to exist within the new storm snow as well as on a hard melt freeze crust which exists up to 80cm below the surface. This crust, which formed at the end of January, is reported to have weak overlying surface hoar and should be treated with caution.Deeper in the snowpack the mid-January surface hoar remains a concern. It can be found down 60-120 cm across the region, but in most places it is about one metre down. In some locations it has reportedly gained quite a bit of strength, but elsewhere it is still producing "sudden" failures in snowpack tests. The mid-December surface hoar layer is now 80 to 140cm below the surface and has become unlikely to fail. The current storm pattern should be a good test to see if it will become active again.
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.
Wet Slabs
Wet Slab avalanches are the release of a cohesive layer of snow (a slab) that is generally moist or wet when the flow of liquid water weakens the bond between the slab and the surface below (snow or ground). They often occur during prolonged warming events and/or rain-on-snow events. Wet Slabs can be very unpredictable and destructive.