North Rockies Avalanche Forecast - February 19, 2021

Stormy conditions are increasing avalanche danger. A tipping point may occur, where riders will start triggering a buried weak layer.

Thursday

Alpine - Considerable
Treeline - Considerable
Below treeline - Moderate

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Friday

Alpine - Considerable
Treeline - Considerable
Below treeline - Considerable

Avalanche Summary

A few wind slab avalanches were triggered by riders in the north of the region on Sunday and Monday, but in general avalanche conditions have been quiet.

The likelihood of triggering new wind and storm slab avalanches will increase quickly as the snow falls and the wind blows Thursday and into the weekend. This is a good time to dial back your terrain choices, with some uncertainty on if/when the buried weak layer will become reactive.

Snowpack Summary

New snow and strong wind will form both wind and storm slabs on Thursday and Friday. The wind is forecast to blow from the southwest, so watch for the deepest and touchiest deposits in lee slopes near ridges at treeline and alpine elevations. The air temperature is forecast to be quite a bit warmer than the past week, so slabs are anticipated to develop quickly.

The snow will load a widespread persistent surface hoar layer. Prior to the storm, the layer was 60 cm near Renshaw, 40 cm deep around Torpy and McBride, and 15 to 25 cm deep further north. Reports suggest this layer is most prevalent around treeline elevations, but likely reaches into the alpine and down into the trees too. It may sit above a crust below 1600 m. The likelihood of triggering this layer will increase as the snow turns into a cohesive slab.

There are presently no deeper concerns in the snowpack.

Weather Forecast

FRIDAY - Cloudy with snowfall, accumulation 5 to 10 cm, 40 km/h southwest wind, alpine temperature -10 C.

SATURDAY - Cloudy with snowfall, accumulation 5 to 10 cm, 40 km/h southwest wind, alpine temperature -10 C.

Travel and Terrain Advice

  • Watch for avalanche hazard to increase throughout the day.
  • Wind slabs are most reactive during their formation.
  • Dial back your terrain choices if you are seeing more than 20 cm of new snow.
  • Watch for signs of instability like whumpfing, hollow sounds, shooting cracks or recent avalanches.
  • Approach steep open slopes at and below treeline cautiously, buried surface hoar may exist.

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A map of the North Rockies. - Avalanche Canada image
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