Avalanche Forecast
Issued: Mar 13th, 2020 4:00PM
The alpine rating is , the treeline rating is , and the below treeline rating is Known problems include Storm Slabs and Deep Persistent Slabs.
astclair,
Avalanche Canada
Intense snowfall and strong winds are building widespread, touchy slabs.
Stick to sheltered, simple terrain and avoid exposure to overhead hazards.
Summary
Confidence
Low - Forecast snowfall amounts are uncertain.
Weather Forecast
Friday night: Cloudy, 5-10 cm of snow, areas in the eastern half of the region favored by the up-slope weather pattern could see up to 20 cm, moderate east winds, alpine temperature -28 C.
Saturday: Cloudy, 5-10 cm of snow, areas in the eastern half of the region favored by the up-slope weather pattern could see up to 15 cm, moderate northeast winds decreasing to light, alpine high temperature -20 C.
Sunday: Mix of sun and cloud, light northeast winds, alpine high temperature -14 C.Â
Monday: Mostly clear, light variable winds, alpine high temperature -10 C, freezing level 1000 m.Â
Avalanche Summary
Strong easterly winds and intense snowfall are expected to form widespread, touchy slabs. Cornices have also grown large with the recent weather, and a cornice failure could trigger a large slab avalanche on the slope below.Â
In the aftermath of the previous storm, there were reports of large (size 2-2.5) explosive-triggered avalanches releasing 20-30 cm deep. In a few cases in the neighbouring Lizard Range and Flathead region, these avalanches were triggered by cornice falls.
Snowpack Summary
Some areas of the South Rockies may see intense and significant snowfall accumulations. Anywhere from 10-40 cm may accumulate by Saturday afternoon, with higher totals favoring up-slope areas in the east of the region. Strong easterly winds will accelerate the formation of touchy slabs, and there is ample snow for transport with this reverse-loading pattern. These conditions may also bring cornices to their breaking point.
A total of 25 to 45 cm of snow from the previous storm has been redistributed by wind or is well-settled. This snow sits on older wind slabs in exposed areas, and a sun crust on solar aspects (south through west facing slopes). Melt-freeze crusts extend up to about 1900 m on other aspects.Â
A thick crust/facet layer currently sits 40-80 cm below the surface and can be found up to 2100 m. The middle of the snowpack is generally strong, but the base of the snowpack contains basal facets that are most prominent in shallow rocky start zones.
Terrain and Travel
- Use increased caution at all elevations. Storm snow is forming touchy slabs.
- Be careful to keep storm day fever from luring you out into bigger terrain features.
- Avoid exposure to slopes that have cornices overhead.
- Be aware of the potential for large avalanches due to the presence of a deep persistent slab.
Problems
Storm Slabs
Some areas of the South Rockies may see intense and significant snowfall accumulations. Anywhere from 10-40 cm may accumulate by Saturday afternoon, with higher totals expected in up-slope areas in the east of the region. Strong easterly winds will accelerate the formation of touchy slabs, and there is ample snow for transport with this reverse-loading pattern. These conditions may also bring cornices to their breaking point.
Aspects: All aspects.
Elevations: All elevations.
Likelihood
Expected Size
Deep Persistent Slabs
Weak snow at the bottom of the snowpack hasn't gone away. Evidence of deep persistent slab avalanches has been focused in the Sparwood-Elkford area over the past month. Human triggering is most likely around steep rocky terrain features, or anywhere the snowpack is thin and weak. Cornices have grown large and loom over many ridge lines, a failing cornice could initiate a deep persistent slab when it impacts the slope below.
Aspects: All aspects.
Elevations: Alpine, Treeline.
Likelihood
Expected Size
Valid until: Mar 14th, 2020 5:00PM
