Expect avalanche danger to rise to High through the day on Thursday. Snow, wind and warm temperatures are likely to overload a persistent slab problem.
Two layers of surface hoar may be found 30 and 90 cm below the snow surface. New snow and warm temperatures will increase reactivity of these layers.
Storm slabs will build and become more reactive as snow accumulates through the day Thursday.
A remotely (from a distance) triggered size 2 persistent slab avalanche was reported on a north aspect at 1350 m on Tuesday. The fracture line was 50 cm deep and ran on a surface hoar layer 50 cm deep.
Additionally there were numerous naturally triggered size 2 persistent slab avalanches running on north aspects suspected to have run on surface hoar buried in early December.
15-30 cm of new snow may accumulate Wednesday night through Thursday.
A buried layer of weak, feathery surface hoar crystals buried mid-December can be found down 35 to 60 cm from the surface. An additional layer of buried surface hoar may exist deeper in the snowpack, roughly 70 to 100 cm below the surface.
The remaining mid and lower snowpack contains several crusts from early in the season that are generally well-bonded to the surrounding snowpack.
Snow depth decreases significantly at lower elevations.
Wednesday Night
Cloudy with snow 5-10 cm, ridgetop wind southwest 30 to 50 km/h, treeline temperature -3 °C, freezing level 900 m.
Thursday
Cloudy with 10-20 cm of snow, ridgetop wind southwest 30-60 km/h, treeline temperature -2 °C. freezing level 1100 m.
FridayCloudy with 10 to 20 cm of snow, ridgetop wind south 40-80 km/h, treeline temperature -2 °C, Freezing level 700 m.
SaturdayCloudy with 1-3 cm of snow, ridgetop wind south 20-30 km/h, treeline temperature -4 °C.
More details can be found in the Mountain Weather Forecast.
