Northwest Coastal

Increasing winds will be driving slab formation at higher elevations on Tuesday. At sheltered elevations where surface hoar exists, storm snow is gradually settling into an overlying slab even without the effect of the wind.

Moderate - Forecast snowfall amounts are uncertain

Tuesday: Cloudy with flurries bringing 3-5 cm of new snow, increasing overnight. Moderate to strong southeast winds. Alpine high temperatures of -7Wednesday: Cloudy with continuing scattered flurries bringing 2-5 cm of new snow, continuing overnight. Light southeast winds. Freezing level to around 600 metres with alpine high temperatures of -4.Thursday: Cloudy with continuing scattered flurries bringing around 3 cm of new snow. Light southeast winds. Freezing level returning to about 300 metres with alpine high temperatures of -7.

Reports from Saturday included one observation of a remotely (from a distance) triggered Size 1.5 storm slab releasing on a steep north-facing roll at 1100 metres. This is suspected to have run on surface hoar buried beneath our recent snow accumulations.Friday's reports included observations of numerous storm slab releases that occurred during last week's storm. These reached to Size 2.5 and were focused on terrain around a 38 degree incline. Both north and south aspects were active. Another older Size 2.5 persistent slab release was also noted. This slab was about 80 cm thick, failed on a low elevation moraine feature on a north aspect, and is suspected to have run on the weak layer from late December.Looking forward, storm snow instabilities should become gradually limited to the most recent accumulations, except where the full depth of recent snow overlies pockets of surface hoar and at higher, more wind-affected elevations. Surface hoar is more likely to exist in sheltered openings at mid elevations. Wind slabs at ridgecrests and around exposed terrain features are an increasing concern.

Stormy weather since the middle of last week has gradually brought about 50-60 cm of new snow to the region. The new snow has buried widespread temperature crusts as well as more isolated surface hoar at mid elevations - both the product inversion conditions early last week. Areas harbouring surface hoar are an increasing concern as the overlying storm snow gradually consolidates into a slab above it. This surface hoar is more likely to exist in sheltered areas at lower elevations. At alpine and upper treeline elevations, shifting winds fed with consistent snowfall have been promoting slab formation on a variety of aspects.Professionals have been monitoring a few layers in the mid snowpack, including crusts and surface hoar layers buried 70-130 cm below the surface. Although these layers have been reactive in recent snowpack tests, only one recent report exists of a persistent slab releasing over the late December weak layer. These layers are a greater concern in the north of the region. The lower snowpack is generally strong, with the exception of areas around Stewart and further north where a basal crust and facets exist.