Avalanche Forecast

Moderate - Due to the number of field observations

THURSDAY: A mix of sun and cloud with isolated light flurries possible, light southwesterly winds, and freezing levels in valley bottoms with alpine temperatures reaching -10 C.FRIDAY: A mix of sun and cloud with isolated light flurries possible, light southwesterly winds, and freezing levels in valley bottoms with alpine temperatures reaching -5 C.SATURDAY: A mix of sun and cloud with isolated light flurries possible, light to moderate westerly winds, and freezing levels rising as high as 2000 m.

Reports from Monday include 2 skier-triggered size 2 wind slab avalanches in the Dogtooth Range. Buried surface hoar beneath the 35 cm thick wind slab is expected to have increased the reactivity of the avalanches which ultimately stepped down to the deeper mid-December facet layer. One avalanche occurred on a northeast aspect while the other occurred on a west aspect. They were both, however, cross-loaded alpine features. Reports from Tuesday include several explosives-triggered Size 2 persistent slab avalanches in cliffy terrain propagating as far as 40m across the slope and stepping down to facets and depth hoar near the ground.Moving forward, lingering wind slabs are expected to remain a concern, especially where the slabs sit over a preserved layer of surface hoar. Wind slabs should be expected in steep, unsupported or convex leeward terrain features. In some places, moderate outflow winds may have caused reverse loading and formed thin new wind slabs in recent days.

25-50 cm of recent snow typically overlies the variable mid-January interface which consists of wind affected surfaces in exposed terrain, surface hoar in sheltered areas, and/or widespread faceted old snow. The bond between the new snow and the old surface is generally gaining strength with colder temperatures that followed the storm but weaknesses are lingering, especially where surface hoar is preserved. Strong southwest winds during the storm and moderate southwest winds following the storm have redistributed the new snow and developed wind slabs in leeward terrain features. The mid-December facet/surface hoar persistent weak layer can be found buried 50-100 cm deep and is generally considered dormant. However, a few storm slab and wind slab avalanches have recently stepped down to this layer in isolated areas. This layer remains an isolated concern for shallow snowpack areas where the layer is closer to the snow surface. With the next storm or period of warming, this layer could wake up and create a more widespread problem.