Choosing moderate-angled slopes with thick, uniform snowpack coverage is a good way to avoid triggering a wind slab or a more destructive failure in the lower snowpack.
Most exposed terrain holds wind slabs of varying vintage, mostly older and less reactive. Importantly, if triggered, wind slabs may step down to deeper layers, causing larger, more destructive avalanches.
A faceted lower snowpack presents a persistent slab problem. This basal layer may be triggered by cornice fall or the weight of a rider in shallow snowpack areas or on steep features where the snowpack transitions from thick to thin.
Aerial observations in White Pass on Thursday included several recent natural persistent slabs to size 2.5, mainly on southeast to southwest aspects. There were also numerous wet loose releases on similar aspects up to size 2 and a few small natural cornice releases triggering small wind slabs. One solar-triggered wind slab stepped down to a persistent weak layer and released a size 2 avalanche.
Check out this MIN report for more detail.
Light flurries have added about 5 cm of new snow to surface hoar that has been growing in the high alpine, although southerly winds may have damaged these unwanted grains on wind-exposed slopes.
New snow has otherwise buried hard, pressed surfaces, wind slab, and sastrugi in exposed terrain. A sun crust should be found on or near the surface of sun-exposed slopes. Forecast winds will lend to these hard surfaces predominating once again. Aside from these less desirable surface conditions, we’ve received reports of good riding on faceted northeast-facing slopes and sheltered terrain at lower elevations.
The lower snowpack is faceted and generally weak, particularly in shallow areas.
Saturday Night
Partly cloudy with isolated flurries and a trace of new snow. 20 km/h south ridgetop wind. Treeline temperature -4 °C.
Sunday
Mostly cloudy. 15 to 40 km/h southeast ridgetop wind, increasing. Treeline high temperature -3 °C.
Monday
Cloudy with flurries continuing from overnight bringing about 5 total cm of snow. 15 to 40 km/h southeast ridgetop wind, easing. Treeline high temperature -1 °C.
Tuesday
Mostly cloudy with scattered flurries bringing less than 5 cm of new snow, mostly overnight. 15 to 20 km/h west ridgetop wind, increasing. Treeline high temperature -2 °C.
More details can be found in the Mountain Weather Forecast.
