An avalanche incident on Monday near Golden reminds us that even under Moderate/Low danger, small windslabs have consequences. Changes to the weather pattern are underway, with warming and trace amounts of new snow. By the weekend, expect avalanche danger to rise along with 20-40 cm of new snow, wind, and warm temps.
Lingering hard wind slabs exist in alpine lee features. Potential failure planes are old weak facet layers, or the Jan 30 layer of facets, sun crusts, and isolated surface hoar down beneath the more recent snow.
A fresh report just in of a fatal avalanche that occurred south of Golden on Monday. A small windslab on a north aspect at 2300 m carried one person a long way (1000 m) down a steep, confined gully with many terrain obstacles.
No new avalanches were reported or observed in the Little Yoho region. Further east, Lake Louise forecasters report many people skiing aggressive lines.
Spotty surface hoar growth up to 7mm has been observed on the snow surface. Beneath that, about 25cm of settled snow sits over the Jan 30 weak layer, with ageing wind slabs lingering in isolated areas. Specific wind-exposed terrain may also feature sastrugi. The mid and lower snowpack remains well-settled, with tree-line snow depths ranging from 120cm to 180cm.
Thursday, clouds move into the region and the warm-up continues with new snow arriving and temperatures reaching above zero in the valley by the weekend. It looks like only a few cm of snow on Thursday - Friday, but we may see 20-40 cm and rain in the valley bottom Friday night -Saturday, elevating the avalanche hazard.
