Confidence
Fair - Timing, track, or intensity of incoming weather is uncertain on Thursday
Weather Forecast
Wednesday: Light flurries with another 3-5cm throughout the day, light to moderate southwesterly winds and freezing levels as high as 1200-1400m. Thursday: Continued light flurries before a warm and wet frontal system makes landfall sometime in the afternoon. Friday: Moderate to heavy snowfall, particularly in the Coquihalla area, with strong southwesterly winds and freezing levels as high as 2000m.
Avalanche Summary
Recent reports include numerous Size 1.0-2.5 natural dry loose and soft wind slab avalanches throughout the region.
Snowpack Summary
Light snowfall on the Duffey and heavy snowfall on the Coquihalla has been redistributed into wind slabs at treeline and above. Surface hoar, facets, and/or crust buried early last week is now around 70cm deep, depending on the area, and remains particularly touchy at treeline. Fresh wind slabs, buried wind slabs, and recent storm snow weaknesses within the top metre are highly reactive to human triggers and have the potential to step down to this persistent weakness, or deeper to another persistent weaknesses buried earlier in the month. Cornices are also large and unstable.
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.