New snow has accumulated over a persistent weak layer and, at least initially, has not bonded well to the old surface. Give the snowpack time to heal, choose low angle terrain and avoid slopes that become sticky or moist.
The 15-25 cm storm snow initially did not bond well to the old weak surface, and the warmer temperatures may continue to make slabs sensitive to triggering. This problem is more likely at upper elevations where warm temperatures impact previously dry snow.
Sun and rising temperatures may produce a moist snowpack by the afternoon.
TUESDAY NIGHT: Cloudy, clearing overnight / moderate northwest wind / ridgeline temperature low -5 / freezing level dropping below 500 m
WEDNESDAY: Mostly sunny with scattered clouds / light northerly wind / ridgeline temperature high +3 / freezing level around 1000 m
THURSDAY: Scattered clouds and incoming flurries beginning to accumulate overnight / moderate southerly wind / freezing level rising to about 1300 m in the afternoon
FRIDAY: Snow, up to 20-30 mm by morning / moderate southerly wind / ridgeline temperature high +1 / freezing level around 900 m
Riders found soft low density storm snow rapidly gaining strength and reactivity as temperatures warmed Monday. Slab avalanches size 1-1.5 and 15-30 cm deep released naturally and were triggered by skiers and explosives in the afternoon. There are some tremendous visuals in this MIN report.
Warm temperatures have transitions 15-30 cm new snow from low density powder to moist snow and crusts. At upper and alpine elevations, dry snow sits on a variety of wind affected surfaces and older crusts.
Click here to check out North Shore Rescue's snowpack update from February 12. It's an excellent snapshot of conditions on the North Shore prior to the advance of the recent storm pattern.
Beneath 15-30 cm recent snow there is a rather unusual mix of facets, thin breakable crust and isolated pockets of surface hoar. There is then 30-40 cm of gradually faceting snow, and then a wide spread and supportive crust underneath.
