***UPDATED***
Reports from late yesterday as well as data gathered early this AM have increased the concern for large natural avalanches.
Two weak layers are buried at a prime depth for human triggering within the top metre of the snowpack. Most avalanches to date have released between 1700 and 2200 m. The likelihood of triggering these layers may increase this weekend as warm and stormy weather returns.
Newly formed storm slabs could be touchy to riders, as they rest on a variety of weak surfaces formed during this past week's cold spell. Slabs may be thickest and touchiest in lee terrain features.
A few small natural and rider-triggered wind slab avalanches released on Thursday in wind-exposed terrain.
The latest persistent slab activity on the buried weak layers described in the Snowpack Summary occurred December 18. There's uncertainty on whether these layers will reactivate during this stormy weather.
Around 40 cm of snow may accumulate between Friday morning and Saturday afternoon. Storm slabs are likely to form as the air temperature warms. The snow may not bond well to previous surfaces that consist of sugary faceted grains, small surface hoar crystals in wind-sheltered areas, hard wind-packed snow in exposed alpine, and a hard melt-freeze crust on steep sun-exposed slopes.
Numerous other problematic layers exist in the top 40 to 100 cm of the snowpack, consisting of surface hoar, faceted grains, and/or a crust. To date, avalanches have been most prominent between 1700 and 2200 m and on all aspects. Read our forecaster blog for managing a persistent slab problem.
Friday Night
Cloudy with snowfall, accumulation 5 to 10 cm, 20 to 40 km/h southwest wind, treeline temperatures -12 °C.
Saturday
Cloudy with snowfall, accumulation 10 to 20 cm, 30 to 60 km/h southwest wind, treeline temperatures -8 °C.
SundayMorning snowfall then a mix of sun and cloud, accumulation 5 to 15 cm, 30 to 60 km/h southwest wind, treeline temperatures -7 °C.
MondayCloudy with snowfall, accumulation 10 to 20 cm, 40 to 60 km/h southwest wind, treeline temperature -2 °C.
More details can be found in the Mountain Weather Forecast.
