Regions
Northwest Inland.
Hazard remains HIGH on Wednesday as the storm ends. Tricky conditions are expected to persist for the next few days.
Confidence
Poor - Due to the number of field observations
Weather Forecast
The storm conditions should end on Wednesday. Overnight Tuesday, the region is expected to see another 5-10mm of precipitation with moderate-to-strong SW alpine winds. On Wednesday, alpine winds wind remain moderate-to-strong but will switch from SW to NW. Light flurries are expected during the day and a temperature inversion is expected to form with a layer of warm air sitting at around 2000m. Similar conditions are expected on Thursday and Friday with a temperature inversion, light alpine winds, and generally dry conditions.
Avalanche Summary
A natural cycle was reported on Monday but observations were limited due to the storm. Reports of unobserved natural activity occurring on Sunday in the south of the region. Also reported was a size 1 skier triggered storm slab avalanche. This released down 15-30cm on a convex roll at treeline. Natural storm and wind slab avalanches are expected to continue on Wednesday and the potential for human triggering remains very high.
Snowpack Summary
Recent winds have been highly variable with strong winds from almost all directions in the last few days. The most recent strong winds have been from SE-SW. Hard and soft wind slabs should be expected on a variety of slopes in open terrain. Rain was reported to almost 2000 m on New Years Day in the southern part of the region. Since then there's been around 30-70 cm of new snow. The new snow may be resting on older wind slabs or surface hoar in northern areas. In the mid-pack you may find another 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. This layer is currently dormant and produces variable results in snowpack tests. I suspect it will remain sensitive to new inputs in the form of new snow and wind for the foreseeable future.
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.