Avalanche Forecast
Issued: Dec 25th, 2019 5:00PM
The alpine rating is , the treeline rating is , and the below treeline rating is Known problems include Persistent Slabs and Storm Slabs.
dsaly,
Avalanche Canada
New snow and wind continue to load a weak layer of surface hoar buried in the snowpack. Step back as snowfall accumulates, its hard to know when the load will be enough to stress this weak layer but we may quickly be reaching a tipping point.
Summary
Confidence
Weather Forecast
Wednesday Night: Snow 10-15 cm. Alpine temperature -6 C. Southwest wind, 25 gusting to 70 km/hr. Freezing level valley bottom.
Thursday: Snow, 15-25 cm. Alpine temperature -3 C. Southwest wind 25-30 km/hr gusting to 70 km/hr. Freezing level 700 m.
Friday: Snow and flurries, 10-15 cm. Alpine temperature -2 C. Southwest wind 30-50 km/hr. Freezing level rising to 600 m.
Saturday: Snow, heavy at times, 20-40 cm. Alpine temperature -1 C. South wind 20-30 km/hr gusting to 50 km/hr. Freezing level 1100 m.
Avalanche Summary
On Tuesday, avalanche control work north of Stewart triggered size 2 storm slab avalanches, this area accumulated 25 cm new snow by Tuesday morning. Several wind slab avalanches to size 2.5 failed naturally from steep, alpine features.
A week ago, natural storm slab to size 2 avalanches were reported in the Shames area, following the snowfall. Further north in the region, explosives triggered storm slab avalanches to size 2. Surface hoar, which the storm snow fell on, was the likely weak layer involved.
Snowpack Summary
Flurries and new snow are being impacted by moderate to strong southwest winds. This has fallen over 10-20 cm low density snow overlies that covers a thin layer of surface hoar and more settled recent snow. In total, 40-70 cm recent snow overlies a more prominent weak layer of surface hoar, old faceted surfaces, and/or a crust on south/southwesterly alpine slopes.
The more prominant layer of surface hoar, down 40-70 cm has been reactive in snowpack tests, providing evidence it is at a tipping point where any additional load (such as a person) could trigger an avalanche on this layer. Heavy snowfall could easily overload this layer. Reports from the Shames area suggest the surface hoar layer is on all aspects, but more prevalent on southeast to southwest aspects around 800-1400 m, and more likely on leeward and sheltered alpine areas.
The lower snowpack is generally considered strong, as there has been very little to report in terms of recent avalanche activity or snowpack test results on deeper layers. Snowpack depths at treeline range from 100-250 cm and taper quickly at lower elevations.
Terrain and Travel
- Fresh snow rests on a problematic persistent slab, don't let good riding lure you into complacency.
- Watch for newly formed and reactive wind slabs as you transition into wind affected terrain.
- Watch for changing conditions today, storm slabs may become increasingly reactive.
Problems
Persistent Slabs
Additional loading from storm snow will stress a weak layer of surface hoar, now anywhere from 60-100 cm deep.
Aspects: All aspects.
Elevations: All elevations.
Likelihood
Expected Size
Storm Slabs
Snow accumulating around the region will be impacted by moderate to strong gust winds. Reactive storm slabs will build and increase through the day.
Aspects: All aspects.
Elevations: All elevations.
Likelihood
Expected Size
Valid until: Dec 26th, 2019 5:00PM
