High elevations where the surface snow may remain dry, and where the melt-freeze crust is thin or absent, is where you're most likely to trigger or encounter avalanches. The field data upon which we build this forecast is limited so please adjust your travel to match the conditions encountered.
Dry snow avalanches might be found at high elevations, especially on shady northerly slopes. South and southwest wind may have formed deeper, more reactive deposits of wind slab on leeward slopes.
Wednesday: Storm slabs (80 cm deep) up to size 3 on northwest through northeast aspects at 2100 m and above. Also smaller storm slabs (30 cm deep) were reported running on the crust, but at lower elevations they broke through that crust and entrained wet snow below.
Since April 9, Kootenay Pass (1780 m) saw about 100 mm that equated to a roughly 30 cm increase in snowpack height. Strawberry Pass (1575 m) was closer to 50 mm and a 15 cm snowpack increase. A lot of rain has fallen in the Kootenay Boundary at most elevations, but there should be dry snow at the highest elevations; but is it 40 cm or 90 cm? The potential for surface instabilities changes significantly between the two!
High elevation shady slopes with recent dry snow is where slab avalanche problems are most likely. This is especially true in wind-loaded areas. This snow now rests on a widespread crust. The exception is 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.
Elsewhere, a thick rain crust or settled moist snow exists at the surface. Avalanche danger will be tied almost exclusively to daytime warming and daily melting of the upper snowpack. The more the crust weakens and the deeper the wetness goes, the greater the hazard from wet loose avalanches.
The mid-snowpack is generally well-settled. In some areas, the lower snowpack has a layer of weak facets near the ground.
Thursday Night
Mainly cloudy with clear periods. Isolated flurries bringing a trace of snow. Light west winds. Freezing level to valley bottom with treeline low around -5 C.
Friday
A mix of sun and cloud with isolated wet flurries or showers. Light northwest winds. Treeline high temperatures around +3 C with freezing levels to 1800 m.
Saturday
Mix of sun and cloud. Light to moderate south winds. Treeline high temperatures around +5C with freezing levels to 2000 m.
Sunday
Cloudy with flurries, accumulations of 5 to 10 cm of snow at high elevations. Alpine temperatures around -1 to -5 C. Moderate but gusting southerly winds.
More details can be found in the Mountain Weather Forecast.
