Regions
Banff Yoho Kootenay.
The next big warm-up comes this way starting on Wednesday evening and continuing through Friday. The snowpack is unlikely to re-freeze overnight, and with continued rain and snow, the conditions will not be great for the next couple of days.
Weather Forecast
A series of warm low pressure systems are moving across BC and AB starting Wednesday night and continuing through Thursday evening. For Thursday expect freezing levels to 2300m, with treeline temperatures at +2. Rain in the valley bottom and snow above 2000m may accumulate 10cm before it stops. Friday will be cloudy and warm.
Snowpack Summary
A settled, mostly dry snowpack exists on shaded aspects above 2300m. On other aspects and below 2300m, expect morning crust and wet snow by mid-day. The base of the snowpack continues to be unstable with a layer of facets failing approximately 60cm above the ground. For this reason, most avalanche prone slopes are out unless they have already slid.
Avalanche Summary
No new avalanches were observed or reported today (teams on the western side of the Wapta and at the Sunshine Village area).
Confidence
Freezing levels are uncertain on Thursday
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.
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.