Warm temperatures, rain below 2200m, and snow at higher elevations may incrementally push the problems closer to the tipping point. Thursday night's warm temperatures, with no freeze, may accelerate the potential for natural activity.
Weather Forecast
For the Icefields, Thursday night will have little overnight freeze and 7mm of precipitation. Friday's freezing level will be 2200m or higher, 7-10mm of rain in valley bottom and 10-15cm of snow in higher elevations by late Friday afternoon. Timing of this is uncertain. Temperatures will cool Saturday to Sunday -3 to -9 degrees Celsius.
Snowpack Summary
Good skiing between 1900-2400m in sheltered areas. Approximately 10-15cm of snow sits on a generally solid mid-pack. The mid-pack is bridging a weak base. The lower snowpack is a combination of weak facets and depth hoar mixed around a Nov rain crust. Below tree line a supportive 20cm melt freeze crust sits above a weak facet layer to ground.
Avalanche Summary
No Patrol or public reports on Thursday. Wednesday's helicopter flight from Jasper to Sunwapta Resort to Maligne lake reported no new avalanches noted and visibility was good. Tuesday's patrol at Bald Hills also did not note any new avalanches. Despite natural activity subsiding forecasters have low confidence in the deep basal weakness.
Confidence
Freezing levels are uncertain on Friday
Problems
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.
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.