Up to 25 cm of storm snow in the west, with only a few centimeters in the east, increases the reactivity of storm slabs. This will raise avalanche danger to high, and avoiding avalanche terrain is strongly recommended.
Snow and wind is creating loose dry avalanches in steep terrain, especially in Yoho, where the largest amounts of storm snow have accumulated.
Storm slabs are forming with the recent snow, wind, and relatively warm temperatures. Newly formed slabs sit on a weak foundation and are expected to be reactive to triggering. At higher elevations, in exposed areas, windslabs will also be forming.
This layer will become more reactive with increased loading from new snow and wind, or surface avalanches that step down. The October and November crusts, on north and south aspects respectively, were still producing isolated slab avalanches down about 50-80 cm over the week.
Lake Louise reported triggering a few size 1 storm slabs with explosives, while Sunshine Patrol noted some size 1 ski cuts near treeline. Otherwise, observations were limited. Once skies clear, evidence of avalanches is expected.
Up to 30 cm of storm snow by Sunday morning is expected to create fresh surface slabs, some of which may fail near the ground. The storm snow will bury a mix of sun crust, wind crust, and facets, sitting atop a faceted snowpack 40–90 cm deep. Two persistent weak layers near the base (the Oct 20 and Nov 9 crusts) continue to produce isolated avalanches and remain a key concern for deeper releases.
Sunday’s temperatures are forecasted to be -5°C in the valley and -15°C at ridge tops. Up to 15 cm of additional storm snow is expected, bringing totals to around 30 cm on the western side of the region. Saturday’s strong winds will ease to moderate by Sunday, with a high-pressure system building in late Sunday into Monday.
