Regions
Kootenay Boundary.
Incoming weather combined with a complex snowpack means this is no time to be pushing into steep terrain. Conservative slope selection is critical to safe mountain travel.
Confidence
Fair - Intensity of incoming weather systems is uncertain on Sunday
Weather Forecast
Overview: A pacific frontal system will push inland on Saturday bringing moisture to the region until early Monday morning. Expect a ridge of high pressure to develop for Monday and Tuesday. Due to significant weather model disagreement for Sunday, I have very limited confidence in forecast snowfall amounts and freezing levels.Sunday: Moderate to heavy snowfall / Moderate westerly winds with extreme gusts / Freezing level between 1700m and 2000mMonday: A mix of sun and cloud / Moderate westerly winds becoming northwesterly with strong gusts / Freezing level at 1500mTuesday: Mainly sunny skies / Light northwest winds / Freezing level at about 1100m
Avalanche Summary
Reports from recent days include a remotely triggered deep persistent slab avalanche with a heavy trigger in a low angle meadow. The slab released on the facet/crust weakness down 80-100 cm on a NW aspect at 2100 m. I expect avalanche activity to include storm slabs with forecast weather.
Snowpack Summary
Up to 25cm of new snow overlies a fairly widespread melt-freeze crust which seems to exist on all aspects up to about 2000m. The bond between the new snow and the crust is expected to be weak, especially where surface hoar crystals (up to 8mm) sit above the crust. With more snow and wind on the way. I would expect the developing to storm slab to increase in size and reactivity.The deeper facet/crust persistent weakness buried at the beginning of February, now down 100-150 cm, is still the primary concern among most professional operators. The interface continues to show "sudden" shears in snowpack tests and has the potential to produce very large and destructive 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.
Deep Persistent Slabs
Deep Persistent Slab avalanches are the release of a thick cohesive layer of hard snow (a slab), when the bond breaks between the slab and an underlying persistent weak layer deep in the snowpack. The most common persistent weak layers involved in deep, persistent slabs are depth hoar or facets surrounding a deeply buried crust. Deep Persistent Slabs are typically hard to trigger, are very destructive and dangerous due to the large mass of snow involved, and can persist for months once developed. They are often triggered from areas where the snow is shallow and weak, and are particularly difficult to forecast for and manage.
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.