Subject: January 12, 2005 Canadian Avalanche Centre PAF South Columbia Region Forecast of avalanche danger beginning Wednesday, January 12, 2005: Day:\Wed. p.m.\Thursday\Friday Alpine:\Considerable\Considerable\Considerable Treeline:\Considerable\Considerable\Considerable Below Treeline:\Moderate\Moderate\Moderate Travel Advisory: New snow with moderate winds caused soft slab formation in the alpine on Wednesday. Snowfall was highly variable across the region. Several weak layers in the upper snowpack, below the recent storm snow are nearing critical load, especially in the Selkirks where a weak layer of surface hoar is buried up to 50 cm deep. This layer is deep enough to produce large human triggered avalanches. Travellers can reduce the risk of triggering avalanches by sticking to terrain less steep than 30 degrees at and above treeline. Avalanches: Many avalanches were reported Wednesday involving slabs in the recent storm snow. Slab thickness was generally 20 ^Ö 40 cm and they were running on all aspects. Most were small and relatively harmless, with a few noteworthy larger destructive events (to size 3) that released naturally or remotely. Snowpack: Storm snow and soft windslabs sit on a weak facetted layer. Contained within the facetted layer are three weak layers of surface hoar. Two of these layers are buried deep enough to be a concern for avalanches. In the Purcells, a weak facetted snowpack is becoming rotten under the influence of continued cold weather. Weather: It^Òs snowed! The Selkirks received 20 ^Ö 30 cms while the mountains west of Golden and Invermere managed 10 ^Ö 20 cm. The snow arrived with moderate SW winds in the northern areas and less in the south. No further new snow is forecast as another surge of arctic air settles in with NW winds at mountaintops. Valley clouds on Friday may camouflage bluer skies and warmer temperatures at higher elevations. Kootenay Boundary Region Forecast of avalanche danger beginning Wednesday, January 12, 2005: Day:\Wed. p.m.\Thursday\Friday Alpine:\Considerable\Considerable\Considerable Treeline:\Considerable\Considerable\Considerable Below Treeline:\Considerable\Moderate\Moderate Travel Advisory: Triggering avalanches in pockets of cohesive drifted snow is probable. Buried weak layers are widespread. What varies is the amount and consistency of the snow above. Previous winds formed pockets of hard and soft wind slabs on most aspects which linger and are now hidden by new snow. Forecast winds may form pillows of drifted snow on east and south facing slopes but cold temperatures may prevent the snow from developing into cohesive slab. Wind protected areas are where the avalanche danger is lowest, and the riding the best. Avalanches: Avalanches released with explosive tests, controlled skier slope testing, accidental human triggering, and naturally. Although the slabs were up to 50 cm thick, most were small enough to pose limited danger because the slab didn^Òt propagate wide. A few were large enough to injure, bury, or kill; I heard one report from the Selkirks of a person popping a cornice and going for a long very nasty ride! Snowpack: By Wednesday afternoon 15^Ö30 cm of new snow was delivered to most areas. The most recent snow hides pockets of hard and soft slabs on most aspects in alpine and open treeline areas. Below this are several weak layers in the top 40^Ö80 cm of the snowpack. Weak layers include granular sugary (faceted) snow, thin layers of slippery surface hoar, and a cranky old crust (with sugary facets above) from December. Weather: It^Òs snowed! More than 25 cm was reported Wednesday in the mountains. The snow arrived with minimal SW winds, but a NW wind is starting up. No further new snow is forecast as another surge of arctic air settles in. Valley clouds on Friday may camouflage bluer skies and warmer temperatures at higher elevations. issued by is, jk