Fresh wind slabs will be easy to trigger as they form. Recent snow will reverse load from northerly winds making windslabs in typically sheltered areas.
Recent snow and wind have formed deep wind deposits in leeward terrain features. They will likely remain reactive Saturday. Watch for shooting cracks in stiffened or drifted snow as an indicator of instability.
A weak layer of surface hoar and/or facets buried ~100 cm deep has produced occasional large, widely propagating avalanches on north to east aspects above 1500 m. Some avalanches have been remotely triggered from hundreds of meters away! A layer at this depth may not show obvious signs of instability. Best to avoid steep or unsupported high consequence alpine terrain.
Friday night
Possible Flurries. Moderate northeasterly wind. -18 ºC.
Saturday
Partly cloudy. Northeast wind 30 km/h except 40 km/h at valley bottom. Alpine temperature -20 ºC.
Sunday
Clear. Moderate to strong northeasterly outflow wind with ridge top speeds nearing 60 km/h. Alpine high -20 ºC.
Monday
Mostly sunny. Strong northeasterly outflow wind. Alpine temperatures climbing to -14 ºC.
More details can be found in the Mountain Weather Forecast.
30-50 cm of recent snow has been stiffened at the surface in the high alpine and transported into wind slabs by moderate winds at all exposed elevations. At lower elevations, the recent snow has settled in Thursday's mild temperatures.
The mid snowpack is generally hard with a couple of crusts buried 60+ cm and 100+ cm deep, these have been problematic on north to east aspects as high as 1700 m, where they are covered in an overlying layer of weak surface hoar crystals. In inland areas these weak layers are closer to the surface and are easier to trigger.
Recent large avalanches are suspected to have run on the deeper of the two layers.
Since the storm cleared up on Thursday, our field team observed a natural avalanche cycle up to size 3 from the highway in the inland areas around Paddy peak. We suspect that some of these may include step-downs to buried weak layers.
Our field team also observed new windslab avalanches up to size 2 and loose snow sluffing from steep alpine terrain around the White Pass.
