Heavy snowfall and extreme wind will create dangerous avalanche conditions at treeline and alpine elevations.
30 to 60 cm of heavy snow could accumulate above the snow line by Friday morning. A natural avalanche cycle will likely occur during the peak of the storm overnight, and could continue on wind-loaded slopes throughout the day. Human triggered slabs will be likely anywhere with more than 30 cm of new snow.
Rain will destabilize surface snow and could produce wet loose avalanches in steep terrain.
No significant avalanche activity has been reported this week, but looking forward we expect natural avalanches to occur during periods of intense precipitation and wind-loading over the next few days.
Heavy snowfall accumulations are likely above 1000 m for the next few days. Rain will soak the snowpack at lower elevations. Avalanches during this period could run on a crust layer that was 20 to 30 cm deep before the storm. Snowpack depths at treeline are roughly 100 cm, while most below treeline terrain is below the threshold depth for avalanches, except for isolated smooth features.
Thursday night
A strong low pressure system brings heavy precipitation that peaks in intensity around midnight. Snow accumulations above 800 m range from 15 to 40 cm, with the greatest accumulations on the western side of the island. Extreme southeast wind with gusts exceeding 100 km/h. Freezing level will be around 1200 m resulting in a mix of precipitation types at treeline.
Thursday
A lull between storms in the morning before another storm arrives in the afternoon, bringing 10 to 20 mm of precipitation by 4 pm. Wet snow is expected above 800 m as freezing levels hover around 1100 m. Extreme southeast wind continues, with gusts in the 70 to 100 km/h range.
SaturdayAnother 15 to 30 mm of mixed precipitation by the late morning, then clearing in the afternoon, 30 to 50 km/h wind from the southeast and freezing level around 1100 m.
Sunday5 to 15 mm of precipitation with freezing level around 1000 m and 50 to 80 km/h wind from the southeast.
More details can be found in the Mountain Weather Forecast.
