Total snowfall amounts for Friday night into Saturday are uncertain. The forecast herein assumes 30+ cm of snow accumulation. New snowfall will likely be reactive to both natural and human activity and it is also loading buried weak layers.
Confidence
Moderate - Intensity of incoming weather systems is uncertain
Weather Forecast
FRIDAY NIGHT: Cloudy with snowfall, accumulation 10 to 20 cm, light to moderate west wind, alpine temperature -10 C.SATURDAY: Cloudy with snowfall, accumulation 5 to 15 cm, light to moderate west wind, alpine temperature -15 C.SUNDAY: Mostly cloudy with light snowfall, accumulation 5 cm, light northeast wind, alpine temperature -23 C.MONDAY: Mostly clear skies, light north wind, alpine temperature -18 C.
Avalanche Summary
On Thursday, there was further evidence of the widespread natural avalanche cycle that occurred in the region during Wednesday's storm. The avalanches were generally within the recent storm snow, around 30 to 60 cm deep, and at treeline and alpine elevations.
Snowpack Summary
More snowfall is expected Friday night into Saturday, with total amounts uncertain but could be upwards of 25 cm or more. The snow may have slab properties where it falls with wind and could be low-density and loose in sheltered areas. This new snow will overly around 30 to 50 cm of recent snowfall, which sits on wind-affected snow in exposed areas and a melt-freeze crust below 1700 m. All this recent snowfall is likely to be reactive to human traffic.The mid-January layer of surface hoar is buried around 50 to 80 cm. The surface hoar is found on shaded and sheltered slopes and is most prominent between 1600 m and 1900 m but has been found up to 2200 m.The middle of the snowpack is generally consolidated. The bottom half of the snowpack is unconsolidated and composed of weak and sugary faceted grains.
Problems
Storm Slabs
Storm Slab avalanches are the release of a cohesive layer (a slab) of new snow that breaks within new snow or on the old snow surface. Storm-slabs typically last between a few hours and few days (following snowfall). Storm-slabs that form over a persistent weak layer (surface hoar, depth hoar, or near-surface facets) may be termed Persistent Slabs or may develop into Persistent Slabs.
Persistent Slabs
Persistent Slab avalanches are the release of a cohesive layer of snow (a slab) in the middle to upper snowpack, when the bond to an underlying persistent weak layer breaks. Persistent layers include: surface hoar, depth hoar, near-surface facets, or faceted snow. Persistent weak layers can continue to produce avalanches for days, weeks or even months, making them especially dangerous and tricky. As additional snow and wind events build a thicker slab on top of the persistent weak layer, this avalanche problem may develop into a Deep Persistent Slab.