New snow and wind have created dangerous avalanche conditions.
Conservative route selection and avoiding overhead hazard is strongly recommended
A buried weak layer may be getting overloaded by the new snow. Slabs failing at this depth will result in large and destructive avalanches.
New snow and strong west winds continue to build touchy storm slabs. Storm slabs have shown wide propagation where they sit over weak surface hoar crystals.
Thursday, numerous large and very large (size 2 to 3) natural and explosive-triggered storm slabs were reported.
Wednesday, a couple skier-triggered slabs size 1.5-2 were reported on west aspects at alpine/treeline elevations. The failure plane was identified as a layer of surface hoar layer beneath the recent storm snow. Natural storm slabs (size 2 to 3) were also observed. Notably, only a few cases failed on the persistent weak layer.
Since the start of the week, 40 to 80 cm has accumulated in the alpine. Some of this new snow fell as rain Thursday night, with the rain/snow line around 1200 m. A crust or wet snow may exist below that elevation.
The storm snow isn't expected to bond well as it sits on a layer of surface hoar, facets, or a thin crust.
Strong winds have been redistributing the new snow at upper elevations, building deeper and more reactive deposits on lee slopes.
A persistent weak layer of surface hoar and facets overlying a crust is buried 90 to 140 cm deep in the southern parts of the region, and up to 240 cm deep in areas north of Stewart. Avalanches failing on this layer will be very large and destructive.
Friday Night
Cloudy with 0 to 5 cm of snow / light rain below 1000 m. 50 km/h northwest ridgetop wind. Treeline temperature -1 °C.
Saturday
Cloudy with 0 to 4 cm of snow. 30 to 50 km/h west ridgetop wind. Treeline temperature -3 °C. Freezing level valley bottom.
Sunday
A mix of sun and cloud. 20 to 40 km/h west ridgetop wind. Treeline temperature -4 °C. Freezing level valley bottom.
Monday
Cloudy with 2 to 6 cm of snow. 50 to 70 km/h southwest ridgetop wind. Treeline temperature -2 °C.
More details can be found in the Mountain Weather Forecast.
