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Avalanche Forecast

Archived

Feb 6th, 2021–Feb 7th, 2021

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

Regions

South Rockies.

Changing wind directions means that wind slabs may be found on any aspect. Pay close attention to conditions as you enter wind exposed areas. Stick to conservative terrain and watch for signs of instability such as whumpfing, cracking and recent avalanches.

Confidence

Moderate - Uncertainty is due to the limited number of field observations.

Weather Forecast

SATURDAY NIGHT - Mainly cloudy with a few flurries, 3-5 cm / moderate northwest wind / alpine low temperature near -20 

SUNDAY - Cloudy with sunny periods and isolated flurries / moderate northwest wind / alpine high temperature near -18

MONDAY - Cloudy with sunny periods and isolated flurries / light northeast wind / alpine high temperature near -23

TUESDAY - A mix of sun and cloud / light northwest wind / alpine high temperature near -19

Avalanche Summary

Recent fresh snow has likely formed reactive wind slabs in wind loaded areas. Changing wind directions will mean that these wind loaded areas may potentially be found on any aspect.

On Friday there was a report of a size 2 explosives triggered wind slab avalanche, as well as a few size 1 human triggered dry loose avalanches. There was also a report of several natural avalanches, potentially up to size 3, a MIN report outlining these can be found here.

On Wednesday, numerous loose-dry natural avalanches were reported up to size 1. 

Snowpack Summary

Up to 45 cm of new snow fell over the past few days. The new snow was accompanied by strong winds, which likely redistributed some of this snow to leeward slopes and terrain features, forming fresh and reactive storm and wind slabs. 

Up to 70 cm of recent new snow sits above a plethora of older snow surfaces. In the alpine and at treeline the buried interface consists of stiff, wind affected snow, facets, surface hoar in isolated areas sheltered by the wind, and a crust on steep solar aspects. Below 1900 m a thick crust can be found underneath the recent snow. 

A solid mid-pack sits above deeply buried decomposing crust and facet layers near the bottom of the snowpack (80-150 cm deep). Though unreactive under the current conditions, steep rocky slopes and shallow snowpacks should still be approached with caution.

Terrain and Travel

  • Avoid freshly wind loaded terrain features.
  • Watch for signs of instability like whumpfing, hollow sounds, shooting cracks or recent avalanches.
  • Avoid terrain traps where the consequence of any avalanche could be serious.
  • Be carefull with sluffing in steep terrain, especially above cliffs and terrain traps.
  • Pay attention to cornices and give them a wide berth when traveling on or below ridges.

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.