While freezing levels remain elevated and winds values continue to transport snow at upper elevations, the forecast team has little confidence in how the deeper instabilities will react to these changes. Although natural avalanche activity has subsided on the deep persistent problem, we still continue to see reports of human triggering.
On Friday, wind values ranged from Moderate to Strong at upper elevations with some areas gusting to extreme. With increased winds and up to 20cm of loose snow available for transport, we expect isolated windslab development in the alpine.
The lower snowpack is comprised of weak facets, with a slab formed over this weakness at treeline and in the alpine. This weak basal layer is uniform across most of the region and has the potential for human triggering and larger avalanches. With warm temperatures over the weekend, we may see some activity on deeper facets below the treeline, especially in the East where temperatures will be the warmest.
No new natural avalanches were observed or reported Friday. lake Louise snow safety produced slab avalanches to size 2 with the use of explosives. These avalanches were failing on reloaded bed surfaces.
Moderate to strong SW winds have created windslab at upper elevations. In protected areas, 10-20 cm of loose snow sits over a denser mid-pack which has formed a slab over the weak facet layers below - this loose snow is getting blown into slabs. The December 17 weak layer is down 25-60 cm and becoming less reactive. The November 16 deep persistent layer of facets and depth hoar is near the base of the snowpack, continuing to show sudden failures.
Warm temperatures will continue Saturday with freezing levels near 1600m. Light flurries are expected on the Western slopes of the region with trace accumulation throughout the day. Ridgetop winds will begin to weaken Friday evening. More unsettled weather is forecasted for Sunday and the start of the week.
