The first big warm up of spring is underway. Loose wet avalanches will be the emerging concern on Saturday. Rising temperatures and weak overnight cooling will bring the North Shore's persistent slab problem back into consideration early next week.
Weather Forecast
Friday night: Cloudy with clear periods. Light southwest winds.Saturday: A mix of sun and cloud. Light southwest winds. Alpine high temperatures around +2 with freezing levels around 1900 metres, increasing overnight.Sunday: Mainly sunny with cloud decreasing over the day. Light northeast winds. Alpine high temperatures around +7 with freezing levels reaching 2500 metres, increasing overnight.Monday: Sunny. Light east or southeast winds. Alpine high temperatures around +10 with freezing levels reaching 3300 metres and remaining elevated overnight.
Avalanche Summary
No new avalanche activity was reported on Wednesday. Explosive control produced small (size 1) slab avalanches on Tuesday. No other avalanches were reported.
Snowpack Summary
Relatively light amounts of moist snow have fallen on a variety of snow surfaces including a crust on steep south slopes and possibly weak surface hoar crystals on sheltered and shaded slopes. The new snow may take a little time to bond, especially on north aspects at higher elevations. A layer of weak and sugary faceted grains sits on a melt-freeze crust about 50 to 120 cm deep. The layer is likely most prominent in the North Shore Mountains and on north aspects. This layer continues to be reactive in snowpack tests. The problem is not typical for the region and we expect this persistent weak layer to linger for some time.The lower snowpack is generally strong.
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.