Tricky conditions are expected in the alpine on Sunday and conservative terrain is recommended. Avoid recently wind loaded terrain and assess the bond between the new snow and the crust before pushing into bigger terrain features.
Summary
Confidence
Moderate - Intensity of incoming weather systems is uncertain on Sunday
Weather Forecast
10-15 cm of new snow is forecast between Saturday evening and Sunday afternoon. Freezing levels are expected to reach around 1300 m in the afternoon and alpine wind is forecast to be moderate from the southwest. Around 5 cm of snowfall is forecast between Sunday evening and Monday afternoon. Freezing levels are forecast to reach around 1200 m in the afternoon and alpine wind is forecast to remain moderate from the southwest. More substantial snowfall is expected on Tuesday with models currently showing 15-25 cm. Afternoon freezing levels are forecast to remain around 1200 m and and alpine wind is forecast to be strong from the southwest.
Avalanche Summary
On Friday, natural activity was limited to one size 1.5 storm slab avalanche on a north aspect and numerous loose wet avalanches up to size 2.5 from south aspects. Explosives and ski cutting triggered numerous storm slabs up to size 2 on north aspects above 2000 m with 10-40 cm thick slabs. On Thursday, a natural size 3 persistent slab avalanche was observed on a northeast aspect at 2100 m elevation. The slab was 200 cm thick and was suspected to have failed on an old facet layer in the middle of the snowpack. Widespread natural avalanche activity occurred during the storm on Thursday including storm slabs up to size 3, mainly from north facing alpine terrain. These slabs were 30-40 cm thick. Explosive control on Thursday resulted widespread storm slabs, some of which stepped down to deeper layers in the snowpack.
Snowpack Summary
30-40 cm of new snow overlies the mid-February crust layer. By the looks of Thursday's avalanche activity, this crust appears to have performed as an excellent sliding surface for our new snow.Beneath the crust, approximately 20-30cm of storm snow from late last week lies over our February 3rd interface. Now down approximately 60-100 cm, this interface comprises a variety of surfaces, including scoured surfaces in wind exposed terrain, surface hoar (size 2-3 mm) in sheltered locations, and sun crust on steep solar aspects. Recent snowpack tests and avalanche control suggest that this layer remains reactive in some areas. The Bonnington Range appears to be one of these areas.Areas with a shallower snowpack (less than about 150 cm) have a generally weak snowpack structure with sugary facets near the ground. This includes shallow alpine slopes and most of the Rossland range. In these areas it is possible for storm slab avalanches to step-down to these deeper weak layers, resulting in large avalanches.
rbuhler,
Avalanche Canada
