Regions
Banff Yoho Kootenay.
Avalanche sightings and/or close calls are still occurring on a daily basis. Cooling temperatures will take some time to start settling down the avalanche activity. It will be some time before we have confidence in the current snowpack. SH
Weather Forecast
A cooling into Friday with freezing levels staying at valley bottoms and alpine temperatures in the -10 to -12 range. A short pulse currently happening Thursday afternoon is forecast to input another 10cm with moderate to strong West winds at upper elevations. Cooler temps, light winds and minimal amounts of snow in the current 3 day forecast.
Snowpack Summary
Fresh windslabs and cornice growth in the alpine with 15 to 35 cm of recent snow and west winds. A 50-100 cm slab overlies the January 6th weak layer of surface hoar, facets and sun crust and snowpack tests indicate an unstable bond between the two. The lower snowpack is facetted and quite weak in thinner areas (<1.5m) and settled in thicker areas.
Avalanche Summary
There have been many close calls in the last week indicating that human triggering remains likely in many areas. Today with warming temperatures there were many loose wet or slab avalanches to size 2 out of steep terrain along the divide, and a large natural avalanche out of the National Geographics in the Lake Louise backcountry.
Confidence
Freezing levels are uncertain on Friday
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.
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.