Regions
Northwest Coastal.
Recently formed wind slabs are expected to remain reactive to human triggering on Wednesday. Use extra caution as you transition into wind affected terrain and watch for signs of recent wind loading in leeward terrain features.
Weather Forecast
A ridge of high pressure is expected to keep the region cold and dry for a couple more days before a storm system arrives on Friday. Wednesday is expected to be sunny with light to moderate outflow winds and treeline temperatures around -15C. A temperature inversion is expected and temperatures will likely be colder at valley bottom than at higher elevations. A mix of sun and cloud is forecast for Thursday with light outflow wind and treeline temperatures around -10C. The storm system is currently forecast to arrive midday Friday and models are showing 5-15 cm by the end of the day.
Avalanche Summary
No new avalanches were reported on Monday. On Sunday, a skier triggered a size 1 wind slab on a northwest aspect at 1400m elevation. The average slab thickness was 20 cm. Explosives also triggered several wind slab avalanches size 1.5-2.5. On Saturday, numerous natural wind slab avalanches up to size 3 were observed in the Bear Pass area. Several of these avalanches released on a basal weakness. In the northern most parts of the region near Bell2 or Ningunsaw, there are still reports as recent as Saturday of natural and skier triggered avalanches to Size 2.5 stepping down to basal facets in the alpine and at treeline.On Wednesday, expect recently formed wind slabs to remain reactive to human triggering. Ongoing outflow winds may continue to add additional load to these wind slabs in places where there is still snow available to be redistributed. A basal weakness continues to create a low probability/high consequence problem for the shallow snowpack areas of the region and very large avalanches remain possible in isolated areas, especially in the north of the region.
Snowpack Summary
Widespread wind affected surfaces are being reported in exposed terrain including scoured surfaces, sastrugi, and hard wind slabs. In areas sheltered from the wind, the surface snow is reported to be faceting and surface hoar is developing. Below around 1100 m elevation, a rain crust can be found near the surface of the snowpack. Deeper in the snowpack, the mid-January surface hoar/facet layer is now typically down 70-100 cm. Recent observations suggest the layer has generally stabilized but isolated weaknesses may still exist, especially where buried surface hoar is still intact. Below this layer, the snowpack is generally strong and well settled. The exceptions are areas around Bear Pass and Ningunsaw where basal facets remain an ongoing concern, especially in shallow snowpack areas.
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.