Regions
Kootenay Boundary.
Be wary of steep south facing slopes, cornices and rising temperatures. Conservative terrain choices should be in your trip planning.
Confidence
Moderate - Timing or intensity of solar radiation is uncertain
Weather Forecast
A pacific cold front is moving into the region bringing cloudy skies and light amounts of precipitation. MONDAY: Cloudy with the freezing level hovering around 1500 m, light south to southwest winds, scattered light rain showers below 2500 m. TUESDAY: Cloudy with flurries and/or light rain, freezing level dropping to 1200 m, winds will be light, south to south west. WEDNESDAY: Light precipitation in the late afternoon, winds forecast to be light from the south, freezing level dipping overnight to 1000 m, then climbing to 1600 m during the day.
Avalanche Summary
Reports of human triggered avalanches have dropped off in the past few days, but there are several reports from yesterday of natural cornice failures producing large (size 2.5 to 3 ) avalanches. These cornice failures triggered the deep persistent weak layer mentioned in the snow pack discussion, buried on Feb 27th. Light to moderate south winds accompanying the incoming precipitation may build wind slabs on lee ( N-NW ) features in the coming days.
Snowpack Summary
Warm temperatures and strong solar radiation have aided settlement and encouraged bonding of the last blast of storm snow. Be aware that there are still multiple buried crusts at treeline and below. Of note are the March 11th crust, and a second crust, (the early March melt/freeze crust) can be found down 50 to 80 cm. The late February (Feb 27th) persistent weak layer of buried surface hoar, is now down 70 to 120 cm. This layer has been the interface for some large avalanches and is worth keeping in mind ( and perhaps looking for by digging a test pit) We suspect that this weak layer is more prominent on northerly (shaded) aspects at and above 1700 m. It may also be found associated with a crust on solar aspects. As the sky clouds over and the freezing level lowers, it's still worth paying attention to moist or wet surface snow . The potential is there for deep weak layers to become reactive. Cornices and exposure to cornice run-outs are definitely still something to be concerned about.
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.