The hazard is starting to increase as a series of atmospheric rivers brings warmer temperatures, extreme winds, and heavy precipitation to the region. As the storm hits Tuesday, we advise backcountry users to stay out of avalanche terrain this week.
Strong to extreme winds, warming temperatures, and 30–50 cm of recent snow—with additional accumulation expected Tuesday—will continue to form widespread wind slabs at treeline and above. Natural avalanche activity related to this problem is expected over the next few days.
A layer of facets and/or surface hoar is buried 40–100 cm deep. As freezing levels rise and heavy precipitation continues this week, natural avalanche activity is expected to increase on this interface.
Strong to extreme winds have the potential to initiate loose dry avalanche activity in steep terrain. Avoid traveling in gullies or exposing yourself to steep overhead terrain.
A couple of skier-triggered avalanches up to size 2.5 occurred on Saturday and Sunday. One was a small wind slab on Bow Peak, and the larger one appeared to fail on a persistent layer down 50-60 cm on Mt Bourgeau.
A significant and widespread natural avalanche cycle is expected to begin Tuesday afternoon and will likely continue through the end of the week.
Expect slab development at upper elevations on Tuesday, loading lee slopes from extreme winds. Beneath this, the March 8 rain crust is down 20-50cm, at 1900 m and below on all aspects, with buried sun crusts at higher elevations. The Jan 24 persistent layer is down 40-110 cm, and is primarily surface hoar at treeline and below in Kootenay and Yoho, and facets at all elevation bands in other areas. Below this, the snowpack is well settled with no significant weaknesses.
A series of atmospheric rivers will move into the forecast region beginning Monday evening. As the system approaches, freezing levels will rise, peaking near 2,300 m. Heavy precipitation is expected, falling as rain at lower elevations and snow at higher elevations. Snow accumulations of 40 to 80+ cm are possible by the end of the week. Winds are forecast to reach extreme levels throughout the storm.
