Forecast snowfall amounts remain uncertain but are expected to come with warm temps and high winds, slabs will develop quickly in lees and could be surprisingly thick.
Weather Forecast
A pacific Low pressure system is pushing hard against the arctic air that persists over Alberta. Waterton is near the margin, but the pacific air should bring moderate snowfall, and increased winds Sunday night through Monday. The arctic high will re-establish itself Tuesday, giving cold clear weather through Wednesday.
Snowpack Summary
Incoming new snow will form fresh storm slabs covering previous surfaces of facetted old low density snow, and windslab in alpine areas lee to west winds. Sugary mid/lower snowpack facets have persisted due to ongoing cold temps. The slab properties over this layer are highly variable, but are most concerning in shallow snowpack areas.
Avalanche Summary
Nearby operations have reported a few small windslabs in the past couple of days. An avalanche involvement in Glacier NP USA on January 5th lead to a fatality. Reports indicate that the avalanche initiated as a soft windslab avalanche which then stepped down in to the basal facets. The victim was not buried.
Confidence
Intensity of incoming weather systems is uncertain
Problems
Storm Slabs
Storm Slab avalanches are the release of a cohesive layer (a slab) of new snow that breaks within new snow or on the old snow surface. Storm-slabs typically last between a few hours and few days (following snowfall). Storm-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.
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.