Regions
Kootenay Boundary.
New snow and wind will be building avalanche hazard over the course of the day on Friday. Keep aware of the changing conditions.
Confidence
Moderate - Forecast snowfall amounts are uncertain on Friday
Weather Forecast
Friday: Cloudy with flurries bringing 10-15 cm of new snow over the day. Moderate to strong south winds. Freezing level to 1600 metres with alpine temperatures of -2.Saturday: Mainly cloudy with isolated flurries and a trace to 5 cm of new snow. Light southwest winds. Freezing level to 1500 metres with alpine temperatures of -3Sunday: Cloudy with sunny periods. Light south winds. Freezing level to 1700 metres with alpine temperatures of -2.
Avalanche Summary
Reports from Wednesday showed our recent snow accumulations triggering naturally as loose moist sluffs from Size 1-2 below treeline. The recent snow also reacted to ski cutting and small cornice releases at higher elevations, producing Size 1 results. Reports from Tuesday indicated snowballing and loose snow avalanches to size 1 from steep terrain on all aspects from tree line and below.Looking forward, similar activity can be expected on Friday as new snow accumulates, wind redistributes it into reactive wind slabs, and rising freezing levels promote loose wet activity at lower elevations. Meanwhile, the lingering possibility of persistent slab reactivity continues to demand a more cautious approach to terrain selection in the alpine.
Snowpack Summary
Last weekend rain soaked the upper snowpack for a second time in a week all the way to mountain tops. Subsequent cooling temperatures then formed a 10-30cm rain crust. In many parts of the region above the 1500m there may now be 15-20cm of new snow sitting on top of the crust. Below the crust expect to see moist or wet snow. The late-February facet / surface hoar interface (70-120 cm deep), the mid-February crust (90-130 cm deep), and basal facets in shallow snowpack areas may still be present at upper elevations and may still be reactive and become a concern as surface crusts break down with daytime warming.
Problems
Wind Slabs
Wind Slab avalanches are the release of a cohesive layer of snow (a slab) formed by the wind. Wind typically transports snow from the upwind sides of terrain features and deposits snow on the downwind side. Wind slabs are often smooth and rounded and sometimes sound hollow, and can range from soft to hard. Wind 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.