Reactive storm slabs are expected at treeline and above.
Stick to conservative terrain and watch for signs of instability.
A weak layer from early March is 100 to 150 cm deep, and the Jan & Feb layers are buried 200 to 300 cm. These remain a concern, especially in northerly alpine terrain. These layers have caused recent very large avalanches in the region.
Up to 20 cm of new storm snow may accumulate at treeline and above by Friday afternoon. Expect to find deeper deposits on north and east-facing slopes, where the wind will load lee slopes.
On Wednesday, numerous, widespread and very large, naturally triggered avalanches (up to size 4) were reported in the region. Many were suspected to have failed on persistent weak layers. On Tuesday, numerous natural and explosive-triggered wet slab avalanches were reported up to size 3.
With more new snow and wind in the forecast, storm slabs and persistent slabs are expected to be reactive to human triggers on Friday.
Recent rain and warming has created a moist/wet upper snowpack 40 to 70 cm deep, except for high elevation terrain, which saw around 5 to 10 cm of new snow. The moist/wet snow will likely form into a crust as temperatures cool and then 5 to 20 cm of new snow falls overtop on Friday. The new snow accompanied by strong southerly wind may build storm slabs at upper elevations. Expect deeper and more reactive deposits on northerly slopes. Persistent weak layers from January, February and March can be found 100 to 160 cm and 200 to 300 cm deep. These layers were very reactive in the recent warming event. Below this, the snowpack is well-settled and strong.
Thursday Night
Cloudy with 1 to 5 cm of snow above 1300 m, possible rain below. 40 to 55 km/h southeast ridgetop winds. Treeline temperature -1 °C. Freezing level 1500 m dropping to 1300 m.
Friday
Cloudy with 5 to 15 cm of snow above 1100 m, possible rain below. 35 to 45 km/h south ridgetop winds. Treeline temperature 0 °C. Freezing level rising to 1500 m.
Saturday
Cloudy with 5 to 15 cm of snow above 1000 m, possible rain below. 25 to 45 km/h southwest ridgetop winds. Treeline temperature -1 °C. Freezing level rising to 1400 m.
Sunday
Sunny. 25 to 35 km/h east ridgetop winds. Treeline temperature +2 °C. Freezing level rising to 1800 m.
More details can be found in the Mountain Weather Forecast.
