Confidence
Fair - Forecast snowfall amounts are uncertain on Thursday
Weather Forecast
On Wednesday expect increased cloud throughout the region. Weather models are disagreeing on snowfall amounts for Thursday/Friday. Some are claiming 5-10cm for each day, while others are looking a lot drier. Stay tuned for more info. Winds are expected to be light to moderate from the northwest trending to light and variable by Friday. Freezing levels are expected to be at about 1100m on Wednesday trending to about 1400m for Thursday/Friday.
Avalanche Summary
Avalanche activity has decreased dramatically since the start of the cooling pattern on Monday. One exception was a size 2 natural slab avalanche that was triggered by cornice fall in the Invermere area on Monday. It occurred on a northeast aspect at 2400m.
Snowpack Summary
Cooling has helped the snowpack to gain considerable strength since the warming on the weekend and a crusts have now developed on most slopes that saw direct sun.On shaded aspects the upper snowpack is also well settled. Below this sits a fairly well bonded mid-pack and riders are feeling increasingly confident in steeper terrain. The mid December facet/surface hoar layer is buried approx. 80 cm on the east side and 200+ cm on the west side. Operators are talking less about this layer as of late. There are also basal facets at the ground which were reactive with the warming last weekend, especially in the thin snowpack parts of the region. Snowpack depths at 2000m sit near 2m deep. If you're traveling around the mountains, it's a good time to take notice of what layers are developing (surface hoar/ crusts/surface hoar on crusts) that may become an issue once buried.
Problems
Deep Persistent Slabs
Deep Persistent Slab avalanches are the release of a thick cohesive layer of hard snow (a slab), when the bond breaks between the slab and an underlying persistent weak layer deep in the snowpack. The most common persistent weak layers involved in deep, persistent slabs are depth hoar or facets surrounding a deeply buried crust. Deep Persistent Slabs are typically hard to trigger, are very destructive and dangerous due to the large mass of snow involved, and can persist for months once developed. They are often triggered from areas where the snow is shallow and weak, and are particularly difficult to forecast for and manage.
Cornices
Cornice Fall is the release of an overhanging mass of snow that forms as the wind moves snow over a sharp terrain feature, such as a ridge, and deposits snow on the downwind (leeward) side. Cornices range in size from small wind drifts of soft snow to large overhangs of hard snow that are 30 feet (10 meters) or taller. They can break off the terrain suddenly and pull back onto the ridge top and catch people by surprise even on the flat ground above the slope. Even small cornices can have enough mass to be destructive and deadly. Cornice Fall can entrain loose surface snow or trigger slab avalanches.