Heavy snowfall, wind, and warm temperatures have primed the snowpack for a natural avalanche cycle.
A combination of heavy precipitation, strong to extreme winds, and high freezing levels suggest a reactive storm slab problem will be developing on Monday night.
Monday Night: Heavy snowfall, 20-65 cm accumulating by Tuesday morning. Alpine temperature -1 C. South wind 40-50 gusting to 100 km/hr. Freezing level 1200 m.
Tuesday: Continuing snowfall, 10-30 cm. Alpine temperature -3 C. Southwest wind 25 gusting to 80 km/hr. Freezing level 900 m.
Wednesday: Snow and flurries, 10-15 cm. Alpine temperature -3 C. Southwest wind 25-45 km/hr. Freezing level 800 m.
Thursday: Flurries, 10-30 cm. Alpine temperature -4 C. South wind 20 gusting to 50 km/hr. Freezing level 800 m.
A few small (size 1) natural storm slab avalanches were observed Monday morning in the region.
Looking ahead, expect new snow and wind to develop reactive slabs and add load to the snowpack, potentially adding stress to a recently buried surface hoar layer.
5-15 cm arriving Monday morning followed by 20-60 cm into Tuesday likely covered a weak layer of surface hoar and/or a crust on south-southwest aspects. (Check out this MIN from Sunday before the snow started.) Strong south-southwest winds are impacting new snow with continued precipitation expected. This has primed the snowpack for a natural avalanche cycle.
This storm snow has covered a layer of 10-30 cm of older snow over a concerning layer of surface hoar that formed in areas sheltered from the wind. Reports suggest this layer can be found on all aspects up to treeline elevations. In the alpine, the recent snow covered hard wind slabs and/or sun crusts on south-facing terrain. The heavy load resulting from this weeks storm may stress this layer.
The lower snowpack is generally considered strong, as there has been very little to report in terms of recent avalanche activity or snowpack test results on deeper layers. Snowpack depths at treeline range from 100-150 cm and taper quickly at lower elevations
