The greatest concern is for alpine north through east-facing, leeward and crossloaded slopes, where both storm slabs and persistent slabs have been most reactive.
Some recent storm slabs have stepped down a crust / facet layer from mid-November buried 50 to 120 cm deep. The layer is widespread in the alpine but has been especially reactive on wind-loaded, north-facing features.
Recent stormy weather formed widespread slabs, which may need another day or two to settle and bond. Additionally, another 10 to 20 cm of new snow in the forecast may form new slabs, especially in leeward terrain.
Numerous size 1 to 2.5 explosive and human-triggered storm slabs were reported in the Whistler/ Blackcomb area throughout the recent storm cycle. A few of these slabs stepped down to the Mid-November crust up to 1 m deep, setting off larger than expected avalanches. Most of these slabs released in leeward north through east facing and crossloaded features.
We expect storm slabs and persistent slabs to remain possible to trigger on Friday
A stormy week has brought up to 80 mm into the region, forming widespread storm slabs that may still be settling and bonding.
10 to 20 cm of snow is forecast to fall overnight and through Friday above 1800 m. The new snow may be accompanied by moderate southwesterly winds forming fresh slabs, especially in leeward terrain.
In the alpine, a hard mid-November crust now lies 60–120 cm deep, depending on aspect, with weak facets both above and below it. Recent storm slabs have in some cases, stepped down to this persistent weak layer. Wind-loaded, north-facing terrain appears to be the most concerning.
A meltfreeze crust caps the surface below around 1800 m. The snowpack rapidly diminishes below 1100 m.
Thursday Night
Cloudy. 2 to 5 cm of snow. 20 km/h outhwest ridgetop wind. Treeline temperature -3 °C. Freezing level 1000 m.
Friday
Cloudy. 5 to 10 mm of precipitation as snow or rain at treeline. 30 km/h southwest ridgetop wind. Treeline temperature 1 °C. Freezing level rising to 1800 m.
Saturday
Mostly cloudy. 10 to 25 mm of precipitation as snow or rain at treeline. 30 km/h southwest ridgetop wind. Treeline temperature 0 °C. Freezing level 1800 m.
Sunday
Mostly cloudy. 45 to 55 mm of precipitation as snow or rain at treeline. 40 km/h southwest ridgetop wind. Treeline temperature 0 °C. Freezing level 1700 m.
More details can be found in the Mountain Weather Forecast.
