Sunday's storm is bringing strong winds and periods of rain and snow.
The danger will increase throughout the day as storm slabs build, becoming more reactive.
A crust / facet layer from mid-November is buried 60 to 100 cm deep. Storm slabs in motion may step-down to this layer causing very large avalaches.
Wet loose avalanches may be possible if the snow surface is moist or wet, especially during periods of rain.
Up to 35 mm of precipitation combined with strong southerly winds is forecast to build reactive storm slabs overnight and throughout Sunday.
On Thursday, several size 2-2.5 explosive-triggered slabs occurred in the Duffey area. They were suspected of having stepped down to the mid-November persistent weak layer.
On Tuesday, a deep and large slab (size 2.5-3) was observed on Matier’s East Ridge. (See photo below) This slab was also suspected of having failed on the persistent weak layer.
The incoming storm is expected to increase the likelihood of both natural and human-triggered avalanches.
15 to 35 mm of precipitation, combined with strong southerly winds, is forecast to fall by 4 pm Sunday. The snow/rain line elevation is uncertain and will likely fluctuate during the storm. Teeline and below could see rain with wet loose avalanches. In the alpine, we expect to see reactive new storm slabs building as the new snow adds up.
A crust with facets, formed in mid-November, is buried around 50 to 100 cm at alpine and treeline elevations. Storm slabs have the potential to step down to this layer.
Snowpack height averages around 100 to 180 cm at treeline and decreases rapidly below 1500 m.
Saturday Night
Cloudy. 5 to 15 mm of precipitation as snow or rain at treeline. 40 km/h south ridgetop wind. Treeline temperature 1 °C. Freezing level 1900 m.
Sunday
Mostly cloudy. 10 to 25 mm of precipitation as snow or rain at treeline. 40 km/h south ridgetop wind. Treeline temperature 0 °C. Freezing level 1800 m.
Monday
Mostly cloudy. 30 to 50 mm of rain at treeline. 40 km/h south ridgetop wind. Treeline temperature 4 °C. Freezing level 2300 m.
Tuesday
Mostly cloudy. 5 to 15 cm of snow at treeline. 30 km/h southwest ridgetop wind. Treeline temperature -3 °C. Freezing level 1300 m.
More details can be found in the Mountain Weather Forecast.
