New snow and wind are combining to build new wind slabs above weak layers of surface hoar and facetted loose snow. Recent sun crusts may act as an easy sliding layer on southerly aspects.
Confidence
Moderate - Intensity of incoming weather systems is uncertain
Weather Forecast
A weak low pressure system is slowly moving from the southern interior towards the northwest. This system is difficult to forecast for snowfall amounts. Generally there is not a lot of moisture associated with this low pressure, however some areas may receive another 5-10 cm of light dry snow overnight and Wednesday. Freezing should remain at valley bottoms for the forecast period. Winds are expected to be light easterly for the forecast period.
Avalanche Summary
No new natural avalanches reported. Some loose snow avalanches up to size 1.0 continue to be reported from steep shaded aspects in the alpine.
Snowpack Summary
Light new snow falls have buried large surface hoar on all aspects at and below treeline and on shaded aspects in the alpine. Easterly winds associated with the new snow may have disturbed surface hoar in the alpine. New snow on southerly aspects may be sitting on a sun crust and/or surface hoar, providing an easy sliding layer. The new snow should be mostly unconsolidated except where it has been re-distributed by the wind. Fresh wind slabs may be sitting on 10-20 cm of facetted snow on all but steep solar exposed aspects. In the southern Purcells, (west of Kimberley), a prominent layer of buried surface hoar has shown to be reactive to human triggers. In this part of the region, it's buried down 40 cm with a cohesive slab above it. Shallow snowpack areas and moraine features may have weak facetted snow near the ground that will require time and some warming to strengthen.
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.