Concern remains for alpine north through east-facing, wind-loaded slopes, where both wind slabs and persistent slabs have been most reactive.
Recent stormy weather and strong southerly winds formed wind slabs in leeward terrain. Cornices also grew during this time and should be given a wide berth.
Recent 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, northerly-facing features.
Numerous size 1 to 2.5 explosive, natural and human-triggered slabs and cornices were triggered in the Whistler/ Blackcomb area throughout the storm cycle this week. A few of these slabs stepped down to the Mid-November crust up to 1 m deep, setting off very large avalanches. Most of these avalanches released in high alpine leeward north through east facing features.
We expect to see more avalanches like these as the next storm arrives.
Saturday is bringing us a bit of a lull before the next big storm blows in Saturday night. Keep an eye out for lingering wind slabs on leeward north and east-facing terrain. These wind slabs also have some isolated potential to step down to a deeper persistent weak layer.
In the alpine, a persistent weak layer formed in mid-November lies 60–120 cm deep, depending on the aspect. This layer is a hard crust with weak facets both above and below it. Some recent slabs have stepped down to this persistent weak layer, creating larger-than-expected avalanches.
A melt-freeze crust or moist snow may be found on the surface below approximately 1700 m. The snowpack rapidly diminishes below 1100 m.
Friday Night
Cloudy. 5 to 10 mm of precipitation as snow or rain at treeline. 30 km/h southwest ridgetop wind. Treeline temperature 0 °C. Freezing level 1700 m.
Saturday
Mostly Cloudy. 2 to 5 mm of rain at treeline. 30 km/h southwest ridgetop wind. Treeline temperature 3 °C. Freezing level rising to 2500 m.
Sunday
Cloudy. 30 to 40 mm of precipitation as snow or rain at treeline. 40 km/h south ridgetop wind. Treeline temperature -1 °C. Freezing level 1500 m.
Monday
Cloudy. 80 to 105 mm of rain at treeline. 50 km/h south ridgetop wind. Treeline temperature 3 °C. Freezing level 2200 m.
More details can be found in the Mountain Weather Forecast.
