Fresh wind slabs might develop with new snow and wind from the southwest. Older wind slabs still linger and can be reactive to human triggers, especially where they sit on feathery surface hoar.
Moderate to strong southwest wind might develop fresh wind slabs where soft snow is available for transport.
Older wind slabs were formed by wind from the northeast and northwest. These slabs might still be reactive to human triggers, especially where they sit on feathery surface hoar.
Triggered wind slabs might step down to deeper buried weak layers and result in larger avalanches.
A layer with weak, feathery surface hoar crystals is buried 25-50 cm deep at sheltered treeline features and in the lower alpine.
A thick crust is buried 60-100 cm deep. Avalanches on this layer will likely reach large sizes.
A few, skier triggered avalanches and isolated natural activity up to size 2 were reported on both layers in the last few days. On Tuesday, explosives triggered avalanches up to size 2 on these layers.
Wednesday night: Increasing clouds, trace of new snow, moderate westerly wind, alpine low -7 °C, freezing level at valley bottom.
Thursday: Cloudy, 5 cm new snow, moderate to strong southwest wind, alpine high -5 °C, freezing level at 500 m.
Friday: Cloudy, 15 cm new snow, strong to extreme southwest wind, alpine high -2 °C, freezing level at 1000 m.
Saturday: Mainly cloudy, 10 cm new snow, moderate southwest wind, alpine high -3 °C, freezing level at 900 m.
There have been a few, skier triggered slab avalanches to size 2 on the two buried persistent weak layers described in the Snowpack Summary in the last few days.
Skiers triggered a small wind slab avalanche in the alpine on Tuesday. Explosives triggered slab avalanches on the two persistent weak layers up to size 2. A small natural wind slab avalanche that likely released on feathery surface hoar was reported as well.
A skier triggered a small wind slab from a distance away on a northeast facing alpine slope on Monday. The avalanche released on feathery surface hoar that was buried in late February. Several natural wind slab avalanches and cornice failures up to size 2 were observed in the alpine.
On Sunday, many small natural wind slab avalanches and one large (size 3) avalanche that released in steep alpine terrain were reported. A small wind slab was triggered by a failed cornice. Skiers triggered small wind slabs on south, east and north facing slopes in the alpine. Loose wet avalanche activity to size 1.5 was observed on steep sun-exposed slopes.
There's a lot going on in the upper snowpack. Careful assessment is recommended.
The snow surface is heavily wind affected in wind exposed areas. There is a crust on the surface below around 1000 m and on solar aspects below around 1200 m.
Feathery, weak surface hoar crystals buried around February 26th are found down 25-50 cm, most prominently at treeline elevations. This layer has been reactive to skier traffic in the last few days.
A thick crust buried in mid-February is now found down 60-100 cm. Skiers triggered avalanches on this layer last weekend, and explosives triggered an avalanche on Tuesday.
The lower snowpack is effectively bridged by the layers above, and we do not expect avalanches to be triggered in the lower snowpack at this time.
