Expect conditions to be very aspect dependant. It is Winter on Northerly aspects with dry snow and very large cornices. And it is Spring on Southerly aspects with moist snow above old crusts.
Confidence
Fair - Timing or intensity of solar radiation is uncertain on Saturday
Weather Forecast
Overnight and Saturday: Mostly clear overnight with alpine temperatures dropping down to -13.0. Light Easterly or Northeasterly winds are expected. Freezing levels rising to about 1300 metres during the day.Sunday: A ridge of High pressure will be centered over the Interior ranges bringing Light Southwest winds and daytime highs of about -6.0 in the alpine. Strong solar radiation and freezing levels rising to about 1500 metres.Monday: The ridge is expected to move Eastwards during the day, but mostly sunny conditions should continue during the day.
Avalanche Summary
Explosives control in several parts of the region resulted in some large cornice falls that released some slab avalanches in the tracks that were restricted to the recent storm snow.
Snowpack Summary
Moist snow may be found on solar aspects up to about 2000 metres. New melt/freeze crusts are developing due to cold clear nights and periods of strong solar radiation during the day. The new storm slab is about 30-50 cms deep, with wind transported pockets that are about 70 cms deep. New cornice growth is reported to be poorly bonded and breaks off easily with light triggers. A weak layer of surface hoar and/or a crust is buried down about 70-120 cms in the alpine and treeline elevations. This surface hoar layer is producing variable results in snow profile tests, and continues to be a concern for professionals.
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.