Regions
Northwest Coastal.
Confidence
Fair - Due to limited field observationsfor the entire period
Weather Forecast
Tuesday: Winds are expected to veer to northwesterlies and ease to moderate in the wake of Monday's frontal system. The temperature inversion is also expected to dissipate with freezing levels returning to valley bottoms. Wednesday and Thursday: The ridge of high pressure is expected to rebuild with a dry outflow pattern.
Avalanche Summary
Recent explosives control produced isolated wind slab avalanches up to Size 2.5 generally on easterly aspects. A few deep slab avalanches up to Size 4 were explosive-triggered in Bear Pass. Many of these involved the entire 200-300cm snowpack running on summer firn in extreme terrain. Full depth glide avalanches have also been running below treeline in the southwestern part of the region.
Snowpack Summary
Hard and soft wind slabs formed by recent moderate to strong westerly winds are lurking on isolated lee features in treeline and alpine areas. Warm temperatures and sun-exposure, and subsequent freezing, formed a surface crust especially on southerly aspects. New surface hoar growth was observed on shady aspects at and below treeline. Surface hoar buried at the end of last week was observed down 20-40 cm in sheltered treeline areas. Widespread glide cracks have opened up in some 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.