Regions
Banff Yoho Kootenay.
The natural cycle has slowed down, but the potential for triggering large avalanches is a very real possibility. Watch for how much freeze you get below treeline Thursday, the snow is isothermal below. SH
Weather Forecast
Trace amounts of snow on Thursday, cloudy conditions and freezing levels up to 1700m. There should be a mild overnight freeze below treeline.
Snowpack Summary
45-70 cm of recent storm overlies a crust from January 30th. The recent precipitation and warmer temperatures have created touchy storm slabs and wind slabs over top of the Jan. 30th interface. The basal facet/depth hoar layers are still active in shallow snowpack areas. A weak freeze below treeline is barely holding isothermal conditions at bay.
Avalanche Summary
Avalanche control over the past four days in Banff, Yoho Park and Kootenay Park have produced numerous avalanches up to size 3 over the last 4 days. Most of the avalanches started dry and turned wet at lower elevations. Also, evidence of a widespread cycle up to size 3.5 throughout the forecast region. Some avalanches running close to full path.
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.
Wind Slabs
Wind Slab avalanches are the release of a cohesive layer of snow (a slab) formed by the wind. Wind typically transports snow from the upwind sides of terrain features and deposits snow on the downwind side. Wind slabs are often smooth and rounded and sometimes sound hollow, and can range from soft to hard. Wind 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.
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.