Avalanche Forecast
Issued: Mar 15th, 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 - Confidence is due to a stable weather pattern; little change is expected for several days.
Weather Forecast
Sunday night: Clear, light northeast winds, alpine temperature -18 C.Â
Monday: Clear, light northeast winds, alpine high temperature -1 C, freezing level 1500 m.Â
Tuesday: Clear, light northeast winds, alpine high temperature -3 C, freezing level 1300 m.
Wednesday: Partly cloudy, isolated overnight flurries with up to 5 cm of snow, light northeast winds, alpine high temperature -11 C, freezing level 800 m.
Avalanche Summary
Numerous small (size 1-1.5) wind slabs were reported on Saturday failing both naturally and from human and explosive triggers. Cornices have grown large with the recent weather, and a cornice failure could trigger a large slab avalanche on the slope below.Â
Cornices and loose wet avalanches may become more reactive with strong solar radiation and rising temperatures forecast for the coming days.
Snowpack Summary
Snowfall totals from the weekend storm varied across the region, with accumulations ranging from 10-25+ cm of snow. Higher amounts fell in the southeastern corner of the region. Strong easterly winds drifted the new snow into wind slabs on lee terrain features in a reverse-loading pattern. A warming trend over the next several days could weaken surface snow and cornices.
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 10-20 cm of new snow into wind slabs on lee terrain features in a reverse loading pattern. These wind slabs may remain possible to human trigger. Cornices may also be reaching their breaking point.
Aspects: East, South East, South, South West, West, North West.
Elevations: Alpine, Treeline.
Likelihood
Expected Size
Loose Wet
Warming 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.
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 16th, 2020 5:00PM
