Avalanche Forecast

Moderate - Uncertainty is due to how buried persistent weak layers will react with the forecast incoming weather. Uncertainty is due to unpredictable avalanche behavior.

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.

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. 

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.

• 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.