Stormy, wet, and mild weather (a pineapple express) will maintain high avalanche danger on Thursday. It's best to wait out the storm or stick to simple, low-angle slopes.
Confidence
Fair - Due to the number of field observations
Weather Forecast
Summary: Mild and wet on Wednesday and Thursday following by cool and dry for Friday and into the weekend. Thursday: 15-25 mm Weds night and 30-45 mm on Thursday. The freezing level is near 2000 m. Ridge winds are moderate to strong from the southwest. Friday: Possible lingering flurries. The freezing level drops to around 500 m. Winds ease to light or moderate. Saturday: Mainly sunny. The freezing level is at valley bottom and ridge winds are moderate from the N-NE.
Avalanche Summary
Numerous size 1-1.5 natural and skier-triggered storm slab avalanches were reported from the Whistler area over the past couple of days, mostly in the upper treeline and lower alpine elevation band. One was an accidentally triggered slab that pulled a skier off a small cliff. Fortunately there were no injuries.
Snowpack Summary
It's likely that snow continues to fall at higher elevations (above 2000 m). Below this elevation recent snowfall has probably been soaked by rain, or will be. 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.