Warm temperatures and sunny skies forecast for the next few days will have a significant weakening effect on the snowpack. If solar radiation is particularly strong, the avalanche danger could rise to HIGH.
Confidence
Fair - Timing or intensity of solar radiation is uncertain on Thursday
Weather Forecast
Generally clear skies are expected for the forecast period as a ridge of high pressure becomes established over much of the province. Winds are forecast to be light to moderate from the northwest becoming southwesterly on Saturday. Daytime alpine temperatures are expected to hover between 0.0 and +5.0.
Avalanche Summary
A widespread natural avalanche cycle took place in recent days in response to heavy snowfall, rising temperatures and high winds. Numerous very large avalanches ( size 3's and 4's ) have been reported. Wind slabs and shallow snowpack areas are areas of high concern. With forecast clear skies and warm temperatures, avalanche activity will likely include loose wet avalanches; however, persistent slab avalanches will remain a very real possibility.
Snowpack Summary
Snowpack depths vary, but in general there is now 200 to 250cm of snow at tree line and as much as 300 cm in select places in the alpine. In some areas we're still dealing with a relatively thin snowpack thanks to a windy early season and strong winds scouring slopes during recent storms. About 100cm of storm snow fell over the past week and has been blown into stiff wind slabs in many areas. Below the recently formed storm slab you may find soft facetted snow and/or surface hoar buried around January 8th. This layer may coexist with a crust at lower elevations. Surface hoar layers buried in November and early December may still be found in the mid to lower snowpack, but are generally considered to be unlikely to trigger.A basal facet/crust combo ( weak sugary snow above and below a crust) near the ground is still a concern in some areas and was likely the reason so many large naturals were reported during and after this last storm cycle.
Problems
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.
Loose Wet
Loose Wet avalanches are the release of wet unconsolidated snow or slush. These avalanches typically occur within layers of wet snow near the surface of the snowpack, but they may quickly gouge into lower snowpack layers. Like Loose Dry Avalanches, they start at a point and entrain snow as they move downhill, forming a fan-shaped avalanche. Other names for loose-wet avalanches include point-release avalanches or sluffs. Loose Wet avalanches can trigger slab avalanches that break into deeper snow layers.
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.