Avalanche Forecast

Issued: Dec 29th, 2019 4:00PM

The alpine rating is moderate, the treeline rating is moderate, and the below treeline rating is low.

Avalanche Canada shorton, Avalanche Canada

Triggering large avalanches is now a low probability/high consequence scenario that can be managed by careful terrain selection.

Summary

Confidence

High - We have a good understanding of the snowpack structure and confidence in the weather forecast

Weather Forecast

SUNDAY NIGHT: Clearing with some clouds, light wind from the northeast, alpine temperatures drop to -12 C.

MONDAY: Mix of sun and cloud, light wind from the northwest, alpine high temperatures around -7 C.

TUESDAY: Periods of snow starting midday with 5-15 cm by the evening, moderate wind from the southwest with strong gusts, alpine high temperatures around -5 C.

WEDNESDAY: Another 5-10 cm of snow overnight then isolated flurries in the afternoon, moderate wind from the southwest, alpine high temperatures around -3 C.

Avalanche Summary

A few small (size 1) human triggered wind slab and dry loose avalanches have been reported since Christmas Day. A widespread cycle of very large deep persistent slab avalanches occurred a week ago (up to size 3.5). The likelihood of triggering a deep persistent slab avalanche has declined since then, but the consequences are severe. A MIN report from Friday north of Fernie (in the South Rockies forecast region) shows the possibility of triggering large avalanches from thin spots in rocky alpine terrain. 

Snowpack Summary

Sheltered terrain has 10-30 cm of soft snow while thin wind slabs have formed at higher elevations. The soft snow overlies a hard rain crust below 1700 m.

Hard snow in the middle of the snowpack sits above weak snow and crusts near the bottom of the snowpack (80-150 cm deep).This weak snowpack structure resulted in very large avalanches last weekend. The likelihood of triggering a deep persistent slab avalanche has declined since then, but could still be possible from thin spots in steep terrain that did not avalanche in the last storm. Another round of avalanche activity on these deep weak layers is possible when the next significant storm arrives.

Terrain and Travel

  • Avalanche hazard may have improved, but be mindful that deep instabilities are still present.
  • Avoid convexities, steep unsupported terrain and rocky outcroppings.
  • Don't let the desire for deep powder pull you into high consequence terrain.
  • Use ridges or ribs to avoid areas of wind loaded snow.

Valid until: Dec 30th, 2019 4:00PM