Regions
Northwest Inland.
Lingering storm instabilities means conditions may remain tricky for a couple days. Rapid warming or sun may increase the likelihood of triggering a slab.
Weather Forecast
A strong warm ridge of high pressure that sits to the SW will interact with the Arctic air to the NE and create a temperature inversion. On Thursday, mostly cloudy conditions with periods of sun are expected across the region with light alpine winds. A layer of above-freezing air is expected to form between 2000 and 2500m. On Friday, the above-freezing air should persist but the valleys will remain cold. The inversion and warm air are expected to break down on Friday night and temperatures should return to normal on Saturday. Winds should remain light on Friday and Saturday. 3-6mm of precipitation are forecast for Saturday.
Avalanche Summary
On Tuesday, we received a report of numerous natural storm slab avalanches up to 1.5 at lower elevations. We have had no new reports from the alpine. A natural cycle was reported on Monday but observations were limited due to the storm. Natural avalanches activity is expected to decrease on Thursday but isolated natural avalanches are possible. The potential for human triggering remains high on Thursday.
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.
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.