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Avalanche Forecast

Archived

Mar 5th, 2021–Mar 6th, 2021

Alpine
Natural avalanches unlikely, human triggered possible.
Treeline
Natural avalanches unlikely, human triggered possible.
Below Treeline
Natural avalanches unlikely.
Alpine
Natural avalanches unlikely, human triggered possible.
Treeline
Natural avalanches unlikely, human triggered possible.
Below Treeline
Natural avalanches unlikely.
Alpine
Natural avalanches unlikely, human triggered possible.
Treeline
Natural avalanches unlikely.
Below Treeline
Natural avalanches unlikely.

Regions

North Columbia.

Human triggered avalanches are possible on steep slopes at higher elevations. Be extra cautious in wind-affected terrain.

Confidence

Moderate - Uncertainty is due to how quickly the snowpack will recover and gain strength.

Weather Forecast

A weak front crosses the region on Friday night.

FRIDAY NIGHT: Cloudy with some scattered flurries and 5-10 cm of new snow, strong south wind, freezing level drops to valley bottom with treeline temperatures dropping to -8 C.

SATURDAY: Cloudy with some isolated flurries, light southwest wind with some moderate gusts, freezing level around 1400 m with treeline temperatures around -5 C.

SUNDAY: Cloudy with some isolated flurries, light south wind, freezing level around 1200 m with treeline temperatures near -5 C.

MONDAY: Mostly sunny, light wind, treeline temperatures around -7 C.

Avalanche Summary

Warm sunny weather between Wednesday and Friday resulted in a widespread cycle of wet loose avalanches on sun-exposed slopes. These were mostly small (size 1-1.5), but a few large (size 2.5) wet avalanches were also reported. Heating also caused some cornice and ice falls. Clouds and cooling temperatures will heal these problems. 

The primary concern this weekend will be wind slabs, both old ones lingering on all aspects and new ones forming on north and east facing slopes. A notable human triggered avalanche from Wednesday provides a good example of the old wind slab problem, as a skier triggered a size 3 avalanche in a steep south-facing couloir in Glacier National Park (MIN report).

Snowpack Summary

A dusting of new snow will accumulate above moist and crusty interfaces that formed during the recent warm up. Some deeper accumulations can be expected in lee terrain features. High shaded terrain will have a mix of soft snow and some old buried wind slabs. The lower snowpack has strengthened over the past week as previous persistent weak layers have become unreactive. The main layers that we had been tracking were a layer of facets that was buried in mid-February (60-100 cm deep) and a layer of surface hoar and/or crusts that was buried in late January (80-120 cm deep).

Terrain and Travel

  • Be careful with wind slabs, especially in steep, unsupported and/or convex terrain features.
  • Look for signs of instability: whumphing, hollow sounds, shooting cracks, and recent avalanches.
  • If you are increasing your exposure to avalanche terrain, do it gradually as you gather information.

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.