Avoid avalanche terrain. Heavy snowfall and strong wind have resulted in dangerous avalanche conditions.
New snow loads will stress weak layers of surface hoar buried 70-150 cm deep. This could result in large avalanches that propagate across terrain features and run far distances. The warm up/cool down temperature swing over the last few days may have destroyed this problematic layer below treeline.
Heavy accumulations of new snow and strong wind have created large unstable slabs at upper elevations. Below treeline, the potential for avalanches will decrease through the day as freezing levels fall and lock up the previously moist snow.
Tuesday night: 5-15 cm of snow with rain possible below 1000 m, light wind from the south, freezing level around 1200 m with alpine high temperatures around +1 C.
Wednesday: 15-20 cm of snow, strong wind from the west, freezing level drops to 500 m and alpine high temperatures drop to -5 C.
Thursday: Scattered flurries, light variable wind, alpine high temperatures around -8 C.
Friday: 5-10 cm of snow, moderate wind from the southeast, alpine high -8 C.
Large natural avalanches up to size 3.5 have been reported in Bear Pass since the start of the storm. The natural storm slab avalanche cycle is likely still underway with ongoing new snow and wind at higher elevations. Below treeline, loose wet avalanches will be the main concern.
As of midday Tuesday, 45 mm of precipitation has fallen in 48 hours. This will have fallen as snow, up to 70 cm at high elevations in the north of the region, while rain soaked the snowpack below treeline. This has resulted in a mix of surface conditions with storm slabs, wind slabs, and wet loose avalanches occurring at different elevations. As the freezing level falls Wednesday, the snowpack will lock up where it was previously moist.
The recent loading has also added stress on the two layers of surface hoar buried 70-150 cm deep. Reports from the Shames area suggest buried surface hoar can be found on all aspects, but is more prevalent on southeast to southwest aspects around 800-1400 m.
