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Avalanche Forecast

Archived

Jan 29th, 2020–Jan 31st, 2020

Alpine
Natural avalanches possible, human triggered probable.
Treeline
Natural avalanches possible, human triggered probable.
Below Treeline
Natural avalanches unlikely, human triggered possible.
Alpine
Natural and human triggered avalanches likely.
Treeline
Natural and human triggered avalanches likely.
Below Treeline
Natural avalanches unlikely, human triggered possible.
Alpine
Natural avalanches possible, human triggered probable.
Treeline
Natural avalanches possible, human triggered probable.
Below Treeline
Natural avalanches unlikely, human triggered possible.

Regions

North Rockies.

Avoiding wind-exposed areas will be a good strategy to reduce avalanche risk and find the best riding. Monitor new snow depth and how the wind is building pillows on more sheltered features; those are the places to avoid.

Confidence

Moderate - Uncertainty is due to how the snowpack will react to the forecast weather.

Weather Forecast

Wednesday Overnight: Wednesday was a very windy and reasonably snowy day; overnight the snow should end and the wind ease to only STRONG from the west with temperatures cooling to around -5 to -10 C.

Thursday: Another pulse of weather with 5 to 15 cm of snow, continued strong southwest winds, and gradually warming temps around -5 C near treeline.

Friday: Continued snow with today's amounts around 20 to 30 cm, continued moderate to strong southwest winds, and warmer. Freezing level rising to 1500 m to 2000 m.

Saturday: Cold front moves through with 5 cm (maybe up to 10 cm) of snow, moderate west winds with strong gusts, and quickly cooling temperatures back to around -10 C with freezing level returning to valley bottoms.

Avalanche Summary

WIndslabs were reported throughout the region, with this MIN report (with great photo) being a good example of the type of problem we're dealing with.

Looking forward, our wind slab problem isn't getting much chance to stabilize. Continued new snow and elevated winds continue to build new pillows on lee slopes and fresh snow that hasn't had time to stabilize on steeper wind-protected slopes.

Snowpack Summary

The upper snowpack reflects the seemingly never-ending pattern of snow & wind; there are widespread storm and wind slabs out there. But there's also lots of places with right-side-up powder that gradually blends into increasingly harder and stronger snow with distance from the surface.

In the mid-pack there's a layer of weaker surface hoar buried in late December remains a concern but is gaining strength. This layer is found across much of the North Rockies region but our focus is around McBride and the McGregors/Torpy. It's a classic surface hoar layer that most prominent in sheltered treeline features 50 to 150 cm below the surface.

Terrain and Travel

  • Be careful as you transition into wind affected terrain.
  • Watch for rapidly changing conditions during periods of heavy loading from new snow, wind, or rain.
  • Watch for signs of instability like whumpfing, hollow sounds, shooting cracks or recent avalanches.
  • Seek out wind sheltered terrain below treeline where you can avoid wind slabs and find great riding.

Problems

Wind Slabs

Wind Slab avalanches are the release of a cohesive layer of snow (a slab) formed by the wind. Wind typically transports snow from the upwind sides of terrain features and deposits snow on the downwind side. Wind slabs are often smooth and rounded and sometimes sound hollow, and can range from soft to hard. Wind slabs that form over a persistent weak layer (surface hoar, depth hoar, or near-surface facets) may be termed Persistent Slabs or may develop into Persistent Slabs.

Storm Slabs

Storm Slab avalanches are the release of a cohesive layer (a slab) of new snow that breaks within new snow or on the old snow surface. Storm-slabs typically last between a few hours and few days (following snowfall). Storm-slabs that form over a persistent weak layer (surface hoar, depth hoar, or near-surface facets) may be termed Persistent Slabs or may develop into Persistent Slabs.