Rapid loading on top of persistent weak layers is expected to create dangerous avalanche conditions over the next few days.Closures of HW 93 (Icefield Parkway) will be in effect starting Jan 29 for control work. 511.Alberta.ca for updated info.
Weather Forecast
Heavy snowfall Monday night, with amounts between 20-40cm possible for the Columbia Icefields area. Moderate SW winds to accompany this snowfall. Pressure rising mid-week as precipitation tapers. Temperatures will drop later in the week as an Arctic ridge establishes itself along the Eastern slopes of the Rockies.
Snowpack Summary
Incoming new snow is building fresh storm slabs and is falling on a persistent slab made up of 3 weak interfaces in the top 30 to 50cm of the snowpack. Depth and distribution of these weak surface hoar/facet layers varies within the terrain; although buried surface hoar has consistently been found in sheltered features at TL.
Avalanche Summary
Avalanche control on Parkers Ridge Friday produced 2 large avalanches, size 2 and 3 on a NE aspect running as a persistent slab. Numerous sloughs observed today from steep rocky terrain.
Confidence
Forecast snowfall amounts are uncertain
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.
Loose Dry
Loose Dry avalanches are the release of dry unconsolidated snow and typically occur within layers of soft snow near the surface of the snowpack. These avalanches start at a point and entrain snow as they move downhill, forming a fan-shaped avalanche. Other names for loose-dry avalanches include point-release avalanches or sluffs.