Regions
Northwest Coastal.
Lingering storm instabilities remain a concern. Investigate local conditions in your area before committing yourself to avalanche terrain.
Weather Forecast
The warm air should break down on Friday. Freezing levels will progressively fall to around 1000m by Friday night. Mostly cloudy conditions are expected during the day and alpine winds are expected to be moderate from the S-SW. On Friday night, a weak trough crosses the north coast and 5-10cm of new snow is possible in many parts of the region. On Saturday, mostly cloudy conditions, light flurries, and light alpine winds are expected. Freezing levels should be around 800m. Sunday should see a mix of sun and cloud, light alpine wind, and freezing levels around valley bottom.
Avalanche Summary
On Wednesday, two natural size 2.5 wind slab avalanches were reported. These occurred on NW-N aspects at around 1600m elevation. Explosives released several wind slabs sized 2-3. On Tuesday, several natural size 2 avalanches were reported in the Terrace area. Natural avalanches activity is generally not expected on Thursday but isolated natural avalanches remain possible. The potential for human triggering is still a major concern for Friday.
Snowpack Summary
Storm snow amounts vary across the region. Since the weekend, some southern areas received close to 1m of new snow and northern areas probably around half that. Strong winds are one common theme in all areas though. Ridge winds were cranking from the SE-SW stripping windward slopes bare and probably forming hard or dense wind slabs in lee and cross-loaded areas. Warm air in the alpine may be melting the snow surface and a surface crust may form when the warm air exits. A buried surface hoar layer in the mid-snowpack may be most prevalent in northern sections like Bear Pass and Ninginsaw Pass. The mid December crust can also be found in the middle of the snowpack and is sandwiched with facets and surface hoar. The November crust down near the bottom of the snowpack is generally well bonded but is still reactive in some test profiles.
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.
Loose Wet
Loose Wet avalanches are the release of wet unconsolidated snow or slush. These avalanches typically occur within layers of wet snow near the surface of the snowpack, but they may quickly gouge into lower snowpack layers. Like Loose Dry Avalanches, they start at a point and entrain snow as they move downhill, forming a fan-shaped avalanche. Other names for loose-wet avalanches include point-release avalanches or sluffs. Loose Wet avalanches can trigger slab avalanches that break into deeper snow layers.
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.