The new storm slab may be easily triggered on wind loaded pockets in the alpine.
Confidence
Fair - Due to limited field observations on Sunday
Weather Forecast
Overnight and Sunday: Light precipitation is expected to continue, bringing 3-5 mm by morning and another 3-5 during the day. The freezing level should drop down to the valley by morning and then rise to about 1100 metres during the day. The winds should remain moderate from the SW.Monday: The moisture should continue to drift in to the region from the West, 4-6 mm is forecast to fall as snow above 1000 metres. Moderate SW winds with strong gusts and alpine temperatures around -7.0Tuesday: Moderate to Heavy precipitation combined with freezing levels rising up to 1400 metres, and moderate to strong Southerly winds.
Avalanche Summary
Some avalanches up to size 2.0 have been reported from explosive control, releasing the recent storm slab down about 40 cms on NE aspects.
Snowpack Summary
The new storm slab is about 30-40 cms deep in the alpine, and is moist and well consolidated at treeline. The storm slab is sitting on a surface hoar layer that developed last week during the clear weather. Another surface hoar layer that developed during mid-november was reported to be active last week. There is a rain crust near the ground that we're calling the early November crust. There are some facets below it, or it may appear as a sandwich of crusts and facets, but it's been reported as unreactive at this time. There is still a sharp transition in snow depth from treeline to below treeline making back-country travel challenging under 1300 m in elevation.
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.
Persistent Slabs
Persistent Slab avalanches are the release of a cohesive layer of snow (a slab) in the middle to upper snowpack, when the bond to an underlying persistent weak layer breaks. Persistent layers include: surface hoar, depth hoar, near-surface facets, or faceted snow. Persistent weak layers can continue to produce avalanches for days, weeks or even months, making them especially dangerous and tricky. As additional snow and wind events build a thicker slab on top of the persistent weak layer, this avalanche problem may develop into a Deep Persistent Slab.