Avalanche Canada shorton, Avalanche Canada

Purcells Avalanche Forecast

Jan 12th, 2020 5:00PM

There are multiple weak layers buried in the snowpack. Heavy snowfall in the southern Purcells could agitate these problems on Monday.

Summary

Confidence

Moderate - Uncertainty is due to the complexity of the snowpack’s structure.

Weather Forecast

SUNDAY NIGHT: Low pressure system passing across the border will result in 15-30 cm of low density snow in the southern Purcells and 5-20 cm in the northern Purcells, moderate wind from the south, alpine temperatures drop to -18 C.

MONDAY: Scattered flurries with 5-15 cm of snow in the southern Purcells and trace amounts further north, clearing in the afternoon, light wind from the west, alpine high temperatures around -15 C.

TUESDAY: Mix of sun and cloudy, light wind from the west, alpine high temperatures around -18 C.

WEDNESDAY: Cloudy in the south and clear in the north, light wind from the west, alpine high temperatures around -18 C.

Avalanche Summary

Over the weekend several small (size 1) wind slab and dry loose avalanches were reported. A few larger (size 2-3) deep persistent slab avalanches were also triggered with explosives in north and east facing alpine terrain, continuing the pattern of large natural and explosive triggered avalanches in the alpine. There have also been a few reports of persistent slab avalanches on a buried layer of surface hoar at treeline elevations over the past week (such as this MIN report).

Snowpack Summary

Low density snow continues to accumulate across the region, with wind slabs likely forming at higher elevations. By Monday afternoon another 20-30 cm of light snow will fall in the southern Purcells and 10-20 cm in the central and northern Purcells. A weak layer of surface hoar that formed in late December remains a lingering concern throughout the region. Reports suggest the layer is about 70 cm deep around Golden, 30 cm deep around Invermere, 70 cm deep in southern parts of the region, and 100 cm deep in western parts of the region. The reactivity of this layer is likely variable throughout the region, so remain suspect of steep open slopes at lower elevations. As usual for the Purcells, the base of the snowpack contains basal facets and it remains possible to trigger these deep weak layers in shallow rocky start zones.

Also, see this Mountain Conditions Report for an update on local conditions in the southern Purcells.

Terrain and Travel

  • Avoid freshly wind loaded features, especially near ridge crests, roll-overs and in steep terrain.
  • Carefully assess open slopes and convex rolls where buried surface hoar may be preserved.
  • Use caution on large alpine slopes, especially around thin areas that may propagate to deeper instabilities.
  • Dial back your terrain choices if you are seeing more than 25cm of new snow.

Valid until: Jan 13th, 2020 5:00PM