We're still seeing smaller wind slab and cornice releases triggering the weak basal snowpack as well as other recent persistent layers. It's not a mistake to focus in on wind slab problems, but make sure to factor in the consequences of a larger, more destructive step down avalanche when you're eyeing up surface hazards.
Southwest winds are redistributing new snow and storm snow into deep pockets at higher elevations. Slabs will likely be the deepest and most reactive on north and east aspects at treeline and above.
Keep in mind that wind slabs have the potential to step down to deeper weak layers, resulting in large and consequential avalanches.
Numerous problematic weak layers exist in the top meter of the snowpack. Recent large persistent slab avalanche observations are strong evidence that these layers are still an active concern in this region. Avalanches on these layers have recently been most prevalent in the southern and southeastern part of the region.
A layer of large and weak facets sits near the base of the snowpack. This layer continues on a sporadic basis to produce very large avalanches that can travel far. Riders are most likely to trigger an avalanche on this layer in steep, shallow terrain, or by triggering a smaller avalanche that could step down to this layer. Your best defence is to stay diligent in choosing low-consequence terrain away from overhead exposure.
Among several natural and human triggered wind slabs and storm slabs (as large as size 2.5), Friday's reports also included a few notable observations of step down avalanches. One of these was a cornice release that triggered a small pocket to the basal snowpack in the South Monashees while another report from the central Monashees details wind slabs in several instances stepping down to one of several midpack layers covered in our snowpack summary.
Reports from Thursday included more observations of the natural cycle described below, in addition to several size 1 (small) to size 2 (large) skier-triggered slabs. Size 1's were up to about 20 cm -deep wind slabs while the lone new size 2 north of Trout Lake failed on a 75 cm-deep freezing rain crust buried in early January.
With clearer weather on Wednesday, a widespread avalanche cycle from within the storm was observed across the region. Several persistent slab avalanches were reported between 2200 and 2400 meters on all aspects. Notable was a size 2 vehicle remote persistent slab avalanche, triggered from 70 m away on a northwest aspect. Several deep persistent slabs were reported to size 4 throughout the Selkirks and Purcells. Numerous wind slab and storm slab avalanches were reported to size 3 on all aspects at treeline and above.
Southwest winds have been redistributing storm snow into 20-30 cm soft slabs in exposed alpine and treeline areas. 40-90 cm of storm snow from the week sits above wind-affected surfaces and a crust that extends up to 1800 m in the northern part of the region and up to 2000 m further south. Small facets may be found above the crust. This layer seems like it could be an emerging concern in the southeast of the region.
Deeper in the snowpack two layers of surface hoar which formed in early January are 60 to 120 cm deep. Although snowpack tests are indicating they may be strengthening, these weak layers are still being watched closely by local operators and may be associated with recent isolated step-down avalanches.
Large and weak facets from November are near the base of the snowpack and although avalanche activity on this basal weakness has been on a bit of a decline, it still figures prominently in the assessments and terrain use (and avoidance) of professionals throughout the region.
Saturday night
Increasing cloud with possible isolated flurries. Light southwest winds.
Sunday
Cloudy with flurries bringing 5-15 cm of new snow by end of day, continuing overnight, with greatest amounts in the north of the region. Light to moderate southwest winds, increasing and becoming strong in the alpine. Treeline high temperatures around -3 with freezing levels to 1300 metres.
Monday
Cloudy with another 10-20 cm of new snow from the overnight period, greatest in the north of the region. Light to oderate southwest winds, easing over the day. Treeline high temperatures around -5.
Tuesday
Cloudy with isolated flurries and up to about 5 cm of new snow, including overnight amounts. Light northwest winds. Treeline high temperatures around -7.
More details can be found in the Mountain Weather Forecast.
