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Considerable avalanche threat in South Purcells
Avalanche Canada reports avalanche danger ratings range between considerable and moderate at this time in the East Kootenay and adjacent regions.
The Southern Purcell Mountains (Purcell Wilderness Conservancy south) has a considerable rating for the alpine and treeline, while below treeline is moderate.
“Wind slab avalanches have the potential to step down to deeper layers,” Avalanche Canada warns due to three persistent weak layers within the snowpack.
“The first is only recently just been buried; it is currently not a concern as the snow above has not formed a slab. It is a surface hoar layer in sheltered terrain and a crust on south facing slopes. The second is a weak layer of surface hoar on shaded aspects and crust on steep solar aspects found down around 50cm.The third is a layer of surface hoar and facets from mid-November which is buried down around 80cm in the region.”
While avalanche activity has tapered off on these layers, they likely remain rider triggerable in specific sheltered terrain features at treeline and below, Avalanche Canada added.
On Tuesday and Wednesday several size one skier triggered wind slab avalanches were reported. These avalanches were on easterly aspects at upper treeline.
“Variable winds mean that wind slab could be found on all aspects at treeline and above. These new slabs will form over facets, surface hoar or a crust meaning they will not bond well. The snow becomes slightly more consolidated after the above mentioned layer until around 50cm below the surface where another weak layer, created in early December, can be found. This layer is made up of surface hoar in sheltered areas and a thin sun crust in open south-facing terrain.
“The layer that is still the main concern, is that of mid-November. It is made up of large surface hoar crystals, facets, and a melt-freeze crust and can be found up to 80 cm deep. This layer has been reactive at treeline between 1,700 to 2,200 m, on all aspects. The snowpack is becoming increasingly complex and faceted.”
All areas comprising the Rocky Mountains in the East Kootenay are listed as having moderate avalanche conditions in the alpine and treeline and low below treeline.
Kootenay and Banff national park areas have considerable ratings in the alpine and treeline and low to moderate below treeline.
Waterton National Park has considerable avalanche danger ratings for the alpine and treeline and moderate below treeline.
Steady snowfall is forecast for the region for the next few days.
If you plan on heading into the backcountry or high country over the holidays, know before you go and check out Avalanche Canada for updates on avalanche conditions.
e-KNOW photo
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