Avalanche Forecast
Regions: Bonnington, Grohman, Kootenay Boundary, Kootenay Pass, Norns, Rossland, South Okanagan, Ymir.
Observations in the region are limited and Tuesday's rain/snow line remains uncertain. Increase your caution as you reach your target of upper elevations where rain-wetted snow or melt-freeze crust is thinner or absent. This is also where recent storm snow is most likely to react to a human trigger.
Confidence
Moderate
Avalanche Summary
A widespread cycle of natural wet loose avalanches occurred with rain in Kootenay Pass on Tuesday. Touchy surface instabilities composed of dry snow were likely widespread at any higher elevations that escaped the downpour.
Looking forward, elevations that saw moderate to heavy rain should see avalanche activity drastically reduce with overnight cooling periods. Areas where new surface crust is very thin and especially where it is absent will likely still harbour upper snowpack instabilities such as wind slabs, or with enough new snow, a more widespread storm slab problem.
Snowpack Summary
By the end of the day Tuesday, parts of the region will see more than 40 mm of precipitation fall. Due to high freezing levels, much of this will be rain with wet or heavy snow at higher elevations. South to southwest winds will likely form wind slabs with the available snow at higher elevations. With enough dry snow accumulation, a more widespread storm slab problem could form.
Whatever dry snow does accumulate will bury awidespread crust, now down 30 to 50 cm, except on north-facing slopes at treeline and above, where the storm snow sits on old, faceted surfaces, and on surface hoar in some sheltered areas.
The mid-pack is generally well-settled.
In some areas, the lower snowpack includes a layer of weak facets near the ground. No recent avalanches have been reported on this layer. However, we continue to track the layer and watch for any signs of it becoming active again.
Weather Summary
Tuesday night
Cloudy with continuing convective flurries bringing 5-15 cm of new snow. Light to moderate southwest winds, easing.
Wednesday
Mainly cloudy with isolated flurries and a trace of new snow. Light northwest winds. Treeline high temperatures around -2 with freezing levels to 1500-1600 m.
Thursday
Sunny. Light west winds. Treeline high temperatures around 0 with freezing levels to 1800 m.
Friday
A mix of sun and cloud with isolated wet flurries or showers. Light southwest winds. Treeline high temperatures around 0 with freezing levels to 1800 m.
More details can be found in the Mountain Weather Forecast.
Terrain and Travel Advice
- Make observations and assess conditions continually as you travel.
- Watch for newly formed and reactive wind slabs as you transition into wind affected terrain.
- Don't be too cavalier with decision making, storm slabs may remain sensitive to human triggering.
- When a thick, melt-freeze surface crust is present, avalanche activity is unlikely.
Avalanche Problems
Storm Slabs
Moderate to heavy rainfall at mid and lower elevations likely led to moderate to heavy accumulations of dry snow and dangerous surface instabilities forming in the alpine and possibly at upper treeline.
Wind slabs are almost certain, but if you find more than 20 cm of new snow on the ground, expect a more widespread and reactive storm slab problem.
Aspects: All aspects.
Elevations: Alpine, Treeline.
Likelihood: Possible - Likely
Expected Size: 1 - 2.5