Regions
Northwest Inland.
Lingering storm instabilities remain a concern. Investigate local conditions in your area before committing yourself to avalanche terrain.
Weather Forecast
The warm air aloft should break down on Friday and alpine temperatures should fall well below zero by the end of the day. Mostly cloudy conditions are expected during the day and alpine winds are expected to be moderate from the SW. On Friday night, a weak trough crosses the north coast and 4-8cm of new snow is possible in many parts of the region. On Saturday, mostly cloudy conditions, light flurries, and light alpine winds are expected. Sunday should see a mix of sun and cloud and light alpine winds.
Avalanche Summary
On Wednesday, a natural size 2 storm slab was reported in the south of the region and isolated natural wind slabs from steep terrain to size 1.5 were reported in the north of the region. On Tuesday, we received a report of numerous natural storm slab avalanches up to 1.5 at lower elevations. 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
40-80cm of new snow fell during the storm system. Strong winds, mainly from the S-SE, have striped windward slopes and built stiff wind slabs in leeward features. Below the storm snow may be a rain crust at lower elevations. In the mid-pack you may find a surface hoar layer, although it appears to be spotty in distribution. Near the bottom of the snowpack is a crust facet combo that was buried in mid-November.
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.