Our persistent weak layer is getting more sensitive and more destructive with each passing storm. Focus too much on new snow problems and you could miss the most critical piece of the hazard.
Flurries and elevated winds should create new wind slabs to manage by Monday morning. Small wind slab releases may step down to weak layers in the upper snowpack to produce larger, more destructive avalanches.
New snow and wind have been working to consolidate reactive slabs over the mid-February weak layer and the late January crust below it. Shaded, wind-loaded areas at higher elevations are the most likely places to trigger this problem.
Periods of sunshine, where they emerge, will destabilize new snow on sun-exposed slopes. Loose avalanches may run naturally or with a human trigger.
Several size 1.5 storm slab/persistent slab avalanches have been reported recently, some have been triggered remotely from up to 10 m away. Two more of these were observed on the Hurley on Saturday. These avalanches have been sliding on the persistent weak layer of facets (now 40 - 60 cm deep) that formed during a clear spell in February. There are reports of wind contributing to slab development over this layer.
5 - 15 cm of new snow, increasing with elevation, should accumulate by Monday morning, bringing us to 30 - 50 cm accumulation on top of various problematic surfaces formed during recent cold, dry conditions. These include weak surface hoar or faceted grains in sheltered, shaded terrain, and sun crusts on sun-affected slopes. This layer was named in several new avalanches on the Hurley on Saturday.
A layer of hard crust buried in late January, currently sitting beneath weak facets and less widespread surface hoar is now 40 to 80 cm deep. Some recent avalanches have failed on it. It's particularly active closer to Whistler.
The snowpack below is strong.
Sunday night
Cloudy with flurries bringing 5 - 15 cm of new snow, increasing with elevation, rain below about 1000 m. 15 to 35 km/h southwest ridgetop wind. Freezing level 1400 m.
Monday
A mix of sun and cloud. 10 to 25 km/h southwest ridgetop wind. Freezing level 1300 m - 1600 m.
Tuesday
Mainly sunny. 5 - 15 km/h variable south ridgetop wind. Freezing level reaching 1700 m.
Wednesday
Sunny. 20 - 30 km/h south ridgetop wind. Freezing level shooting to 2300 m.
More details can be found in the Mountain Weather Forecast.
