Avalanche Forecast
Issued: Mar 14th, 2020 4:00PM
The alpine rating is , the treeline rating is , and the below treeline rating is Known problems include Wind Slabs, Loose Wet and Deep Persistent Slabs.
astclair,
Avalanche Canada
Strong northeast winds have formed wind slabs on atypical slopes. Sunny skies and a warming trend could start to weaken sun-exposed slopes and cornices.
Summary
Confidence
Moderate - Uncertainty is due to how the snowpack will react to the forecast weather.
Weather Forecast
Saturday night: Decreasing cloud, light northeast winds, alpine temperature-25 C.Â
Sunday: Mix of sun and cloud, light northeast winds, alpine high temperature -8 C.Â
Monday: Mostly clear, light variable winds, alpine high temperature -1 C, freezing level 1300 m.Â
Tuesday: Mostly clear, light northeast winds, alpine high temperature 0 C, freezing level 1800 m.
Avalanche Summary
Numerous small (size 1-1.5) wind slabs were reported on Saturday failing both naturally and from human and explosive triggers.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.Cornices have grown large with the recent weather, and a cornice failure could trigger a large slab avalanche on the slope below.Â
Snowpack Summary
Snowfall totals varied across the region, with some areas accumulating 10-20 cm of snow. Strong easterly winds drifted the new snow into wind slabs on lee terrain features in a reverse-loading pattern.
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
- Stay off recently wind loaded slopes until they have had a chance to stabilize.
- Minimize exposure to sun-exposed slopes when the solar radiation is strong.
- Use extra caution around cornices: they are large, fragile, and can trigger slabs on slopes below.
- Be aware of the potential for large avalanches due to the presence of a deep persistent slab.
Problems
Wind Slabs
Strong easterly winds have drifted the new 10-20 cm of snow into wind slabs on lee terrain features. This wind direction is atypical, so you may find wind slabs in terrain features that don't typically have them.
Aspects: East, South East, South, South West, West, North West.
Elevations: All elevations.
Likelihood
Expected Size
Loose Wet
Rapidly rising temperatures and intense solar radiation may initiate wet loose avalanches and weaken cornices. This activity is likely to be most prominent on steep slopes that receive direct day-time solar radiation (slopes that face south through west). Minimize exposure to steep, sun-exposed slopes and cornices on Sunday.
Aspects: South East, South, South West, West.
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 15th, 2020 5:00PM
