Careful decision making is still required with lingering persistent weak layers. These layers are not always obvious and are variable across the terrain.
Weather Forecast
The low pressure system that brought us 10cm is moving out of our region & being replaced by a high pressure ridge. No significant snowfall today with freezing levels rising to 1400m. Winds will be light from the SW with occasional gusts to 45km/h. The stormy weather returns next week with 20-30 cms of snow forecast for Tuesday-Thursday morning.
Snowpack Summary
12cm of snow overnight and 30km/hr South winds have built variable soft slabs in the alpine and exposed treeline areas. Below 2000m, 20cm sits on a supportive crust. Storm instabilities down 30-60cm are present but becoming less reactive. Persistent layers exists down 150cm (February crust) and near the base of the snowpack (November crust).
Avalanche Summary
2 size 2.5 avalanches were observed from the highway corridor on the north face of Mt MacDonald. These slides were triggered during a spike in wind speed late in the day on March 22nd. There have been reports of cornices failing and triggering large slabs in steep terrain in areas near Glacier National Park.
Confidence
Due to the number and quality of field observations
Problems
Wind Slabs
Wind Slab avalanches are the release of a cohesive layer of snow (a slab) formed by the wind. Wind typically transports snow from the upwind sides of terrain features and deposits snow on the downwind side. Wind slabs are often smooth and rounded and sometimes sound hollow, and can range from soft to hard. Wind slabs that form over a persistent weak layer (surface hoar, depth hoar, or near-surface facets) may be termed Persistent Slabs or may develop into Persistent Slabs.
Persistent Slabs
Persistent Slab avalanches are the release of a cohesive layer of snow (a slab) in the middle to upper snowpack, when the bond to an underlying persistent weak layer breaks. Persistent layers include: surface hoar, depth hoar, near-surface facets, or faceted snow. Persistent weak layers can continue to produce avalanches for days, weeks or even months, making them especially dangerous and tricky. As additional snow and wind events build a thicker slab on top of the persistent weak layer, this avalanche problem may develop into a Deep Persistent Slab.