Rapid cooling should help stabilize the snowpack and lower the avalanche danger heading into the weekend.
Confidence
Fair - Due to the number of field observations
Weather Forecast
Friday: Temperatures start to plummet early with freezing levels dropping to 500 m by mid-day. We could see a pulse of light snow (5 cm) in the afternoon. Winds ease. Saturday: Mainly sunny. The freezing level is at valley bottom. Winds are light to moderate from the NE. Sunday: Sun and cloud. The freezing level remains at valley bottom. Winds are light from the W-NW.
Avalanche Summary
Numerous loose wet and wet slab avalanches up to size 2 were reported near Whistler on Wednesday as temperatures spiked and rain started to fall. It's likely that natural activity continued overnight with the potential for larger slab avalanches at higher alpine elevations. Natural activity should taper off on Friday if temperatures cool as forecast.
Snowpack Summary
It's likely that wet snow continues to fall at higher elevations (above 2000 m). Below this elevation recent snowfall has probably been soaked by rain. As temperatures drop later this week I would expect a new crust to form, possibly with some fresh snow on top. An old snow surface of weak facets sitting on a crust is now down as much as 50-60 cm at treeline elevations and deeper in the alpine. Initial reports suggest this weakness is most pronounced slopes at upper treeline and lower alpine elevations. However, as we begin our forecasting season, we are working with limited information from the field. Check the bond of the snowpack at this level and take a cautious approach as new snow builds deeper above this layer.
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.
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.