Highly variable snowfall from Tuesday's storm set up an equally variable wind slab problem over the region. Expect new snow to shed easily from steeper slopes as warming and sunshine take effect on Wednesday.
Weather Forecast
Tuesday night: Mainly cloudy with isolated flurries and a trace of new snow. Light west winds shifting to east.Wednesday: A mix of sun and cloud. Light east winds. Alpine high temperatures around -3 with freezing levels to 1800 metres.Thursday: A mix of sun and cloud. Light northeast winds. Alpine high temperatures around -2 with freezing levels to 1900 metres.Friday: Mainly sunny. Light variable winds. Alpine high temperatures around 0 with freezing levels to 2100 metres.
Avalanche Summary
Reports from Monday showed included a few more 12-24 hour old observations of avalanches induced by recent warm temperatures. These included a size 2.5 glide slab at 2200 metres, a size 2 (large) loose wet avalanche at 1900 metres, and several small (size 1) wet slabs at 1250 metres. Looking forward, avalanche danger will remain linked with daytime warming and especially sun exposure. New snow from Tuesday's storm will be the first to shed from steeper slopes as warming takes effect.
Snowpack Summary
Variable new snow amounts of a trace to 20 cm have accumulated above a surface of melt-freeze crust in most areas above 1500 metres, with the exception of limited north aspects above 2000 metres, where it may have landed on the last dry snow that remained after last week's warm up. Below about 1500 metres, it has buried variably isothermal (slushy) and crusty surfaces. Precipitation as rain has continued to saturate the snowpack that is for the most part isothermal and disappearing rapidly below about 1100 metres.The mid snowpack is generally consolidated and strong, but exceptions may exist on north aspects above 2000 m, where a gradually strengthening layer of faceted grains buried 40 to 60 cm deep may still be preserved below an overlying slab of old and hard wind-affected snow.The base of the snowpack is composed of weak faceted snow which may coexist with a melt-freeze crust. One very large persistent slab was reported to have failed at this layer during last week's warming event.
Problems
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.
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.