Regions
Kootenay Boundary.
Weather Forecast
Synopsis: A frontal system moves through the region late on Tuesday bringing light snowfall Tuesday night. On Wednesday afternoon and Thursday, a ridge of high pressure builds in the region.Tuesday: Flurries. Light SW winds increasing at the end of the day. Freezing level around 1000m.Wednesday: Around 5 cm new snow, which should end by noon. Clearing in the afternoon. Freezing level around 1200m. Strong westerly winds in the morning, diminishing through the day.Thursday: Dry and sunny. Freezing level 800m in the afternoon. Light NW winds.
Avalanche Summary
There were two size 1 human-triggered avalanches reported from Saturday on north aspects in recent new snow with crowns of 10-20 cm. Loose snow avalanches were reported over the weekend on steep solar aspects. On Sunday, several small (size 1) human-triggered avalanches were reported in buried surface hoar from just outside the region on north aspect slopes.
Snowpack Summary
The snow surface consists of a sun crust, surface hoar, or a dusting of new snow. Below this approximately 15-20 cm of recent storm snow has been redistributed into soft wind slabs at higher elevations. The new snow overlies a gamut of old surfaces which include old wind slabs at higher elevations, fairly widespread surface hoar, and a melt-freeze crust on previously sun-exposed slopes. This interface will be something to watch as the overlying slab develops. About 35-50cm below the surface is another interface of surface hoar or a sun crust that was buried on Jan 23. It is hard to find in some areas and seems to be gaining strength where it is found, but this weakness is still on the radar of professionals in the region. The snowpack below this is generally well settled and bonded.
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.