Avalanche Canada shorton, Avalanche Canada

Purcells Avalanche Forecast

Jan 11th, 2020 5:00PM

Low density snow in the forecast will improve the riding, but keep in mind there are still multiple weak layers buried deeper in the snowpack.

Summary

Confidence

High - The snowpack structure is generally well understood.

Weather Forecast

SATURDAY NIGHT: Scattered flurries with up to 10 cm of low density in the southern Purcells and 5 cm in the northern Purcells, moderate wind from the southwest, alpine temperatures drop to -15 C.

SUNDAY: Scattered flurries with 5-10 cm of low density snow, light to moderate wind from the south, alpine high temperatures around -10 C.

MONDAY: Flurries with 5-15 cm of snow overnight and another 5 cm throughout the day, light wind from the southwest, alpine high temperatures around -15 C.

TUESDAY: Mostly cloudy with isolated flurries, light wind from the southwest, alpine high temperatures around -15 C.

Avalanche Summary

Over the past few days avalanche activity has been limited to small wind slab avalanches (size 1-1.5), primarily on north and east aspects. The most recent natural avalanche cycle occurred on Wednesday, when many large and very large avalanches (size 2-3) were reported. Several of these avalanches ran on deep persistent weak layers in alpine terrain (above 2400 m) while others ran on a buried layer of surface hoar at treeline elevations (such as this MIN report that provides a helpful example terrain that is likely to harbor the persistent slab problem). A few more large deep persistent slab avalanches were triggered with explosives on Thursday.

Snowpack Summary

Low density snow continues to accumulate across the region. Open terrain at higher elevations may be affected by moderate wind from the southwest and have freshly formed wind slabs. 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.

Terrain and Travel

  • Avoid freshly wind loaded features, especially near ridge crests, roll-overs and in steep terrain.
  • Use caution on large alpine slopes, especially around thin areas that may propagate to deeper instabilities.
  • Carefully assess open slopes and convex rolls where buried surface hoar may be preserved.

Valid until: Jan 12th, 2020 5:00PM