Regions
Kootenay Boundary.
It looks like we are headed into our first large avalanche cycle of the 2011/12 season. The new snowfall is very exciting but please remember to play safe and avoid avalanche terrain through times of dangerous avalanche conditions.
Weather Forecast
Tonight and Tuesday: A strong system typically known as a Pineapple Express is moving across the province from the coast. It will bring moderate to heavy amounts of precipitation accompanied by strong south westerly winds. Freezing levels could rise up to 1900m as this pushes through and falling to lower elevations later in the forecast period. This will persist through to Wednesday. Thursday and Friday: Unstable conditions throughout light precipitation expected with freezing levels lowering.
Avalanche Summary
Observations are extremely limited at this time. No new avalanches have been reported from yesterday or today. The next few days will hold a different story. I'd expect widespread avalanche activity. They may react as storm slab instabilities with potentially triggering any weaknesses lower in the snowpack.
Snowpack Summary
Light snowfall amounts 5-10cm overnight in the southern part of the region. 10-30cm of new snow has fallen last friday and saturday, significantly more at the south end of the region. Snowpack depths are likely in the 60-80cm range at about 1600m and about 130 cms at 2000m. In the upper snowpack, wind slab and storm snow instabilities exist around lee features and ridgelines. There are also reports of a thin rain crust in the upper 50cm. With the "Pineapple Express" on it's way we may see an abundance of new snow at higher elevations. The accumulations could surpass our current total snowpack HS.
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.
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.