Avalanche Forecast
Issued: Feb 19th, 2023 4:00PM
The alpine rating is , the treeline rating is , and the below treeline rating is Known problems include Wind Slabs and Deep Persistent Slabs.
jpercival,
Avalanche Canada
Winds slab development is on the rise and as the wind direction changes, expect to find wind slabs on all aspects. Take time to ensure when transitioning into areas directly below ridgetops you are assessing both the depth and bond of this new wind-transported snow.
A thin and very tricky snowpack that harbors a deep persistent slab avalanche is prevalent in this region. Employ travel techniques that focus on conservative terrain selection and minimize exposure to thin rocky and steep terrain features.
Avoid shallow rocky areas where the snowpack transition from thick to thin and triggering deep persistent layers is more likely.
Summary
Confidence
Moderate
Avalanche Summary
On Saturday, ski cutting performed by ski guiding operations produced small (size1) soft slab avalanches with the additional observation of small (size1) loose dry avalanches on very steep east aspect terrain. Reports from Mnt Chief Pascall indicate wind-affected snow on exposed terrain with small (size 1) wind slabs initiated with ski cutting. See MIN for photos and further details.
On Friday, Small (size 1) loose dry avalanches were observed in many steep rocky areas.
On Tuesday, several large natural deep persistent slab avalanches were reported near South Chilcotin Mountains Provincial Park and the Birkenhead area. The avalanches were up to size 3 and were likely triggered by cornices or wind. See this MIN for photos of a few of the avalanches.
Numerous small loose dry avalanches were reported to size 1.5 on all aspects. A skier accidental size 1 wind slab avalanche was reported in northeast-facing alpine terrain.
On Monday afternoon, search and rescue technicians responded to a fatal avalanche incident north of the Sea to Sky region. The avalanche is believed to have occurred on Saturday and was initiated in a shallow rocky area. See the MIN for more details.
Snowpack Summary
Up to 30 cm of recent storm snow accumulation is being actively redistributed by moderate southerly winds. The expected wind direction of strong north through northwest winds will begin to load and cross load south aspect terrain Expect on all aspects this new snow to be redistributed over wind-affected surfaces at higher elevations and a crust at lower elevations. On steep solar slopes at lower elevations, a sun crust can be found on the surface.
A melt-freeze crust from late January is found down 60-80 cm. At the moment this layer appears to be gaining strength though in isolated areas small facets are still found surrounding the crust.
There is a widespread weak layer of large sugary of facets at the bottom of the snowpack. This layer has recently resulted in a handful of large destructive avalanches. These avalanches seem to be concentrated in the northern half of the region however the layer is found throughout. Snowpack depths around treeline range between 150 to 250 cm.
Weather Summary
Sunday Night
Cloudy with some clearing isolated light flurries, 1 to 5 cm of accumulation. Winds northwest 70 km/h. Treeline temperature -2 °C. Freezing level 1000 m.
Monday
Cloudy with isolated flurries, 1 to 5 cm of accumulation. Winds northwest 30 km/h. Treeline temperature -1 °C. Freezing level rising to 1500 m mid-day.
Tuesday
Cloudy with afternoon clearing, light snowfall, 5 to 10 cm of accumulation. Winds northwest 30 km/h. Treeline temperature -5 °C. Freezing level descending to 200 m.
Wednesday
Mostly clear, no precipitation is forecast. Winds northeast 10 km/h. Treeline temperature -12 °C. Freezing level descending to 0 m.
More details can be found in the Mountain Weather Forecast.
Terrain and Travel Advice
- Pay attention to the wind, once it starts to blow fresh sensitive wind slabs are likely to form.
- Recent wind has varied in direction so watch for wind slabs on all aspects.
- Avoid steep, rocky, and wind effected areas where triggering slabs is more likely.
- In areas where deep persistent slabs may exist, avoid shallow or variable depth snowpacks and unsupported terrain features.
Problems
Wind Slabs
New northerly winds are building new and reactive wind slabs in exposed alpine and upper treeline features. Continue to use caution on lee features and watch for areas that have been reverse-loaded and cross-loaded.
Southwesterly winds have previously distributed available snow into wind slabs on north and east slopes in the alpine and upper treeline. Wind slabs may be sitting on a crust making them especially reactive to light triggers such as skiers.
Increasing wind and available snow for transport will continue to build cornices at the ridgetop.
Aspects: All aspects.
Elevations: Alpine, Treeline.
Likelihood
Expected Size
Deep Persistent Slabs
A layer of large and weak facets sits near the base of the snowpack. This layer is most likely to be problematic in steep, unsupported, wind-loaded terrain or by first triggering a layer further up in the snowpack. Avoid shallow rocky snowpack areas where the risk of triggering these layers is higher.
Aspects: All aspects.
Elevations: Alpine, Treeline.
Likelihood
Expected Size
Valid until: Feb 20th, 2023 4:00PM
