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Avalanche Forecast

Archived

Jan 29th, 2020–Jan 30th, 2020

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

South Rockies.

Winds slabs maintain an ongoing concern as steady winds continue to redistribute loose snow. Watch for reactive pockets around steep rolls and ridge features.

Confidence

Moderate - Confidence is due to a stable weather pattern with little change expected.

Weather Forecast

Wednesday night: Mostly cloudy with isolated flurries. Alpine low temperature -8 C. Moderate west winds.

Thursday: Mix of sun and cloud. Alpine high temperature -6 C. Moderate west winds. Freezing level climbing to 1500 m.

Friday: Mix of sun, cloud and flurries, 5 cm. Alpine high temperature 0 C. Moderate southwest winds with strong gusts. Freezing level rising to 2000 m.

Saturday: Flurries and snow, 10-15 cm. Alpine high temperature -1 C. Moderate southwest wind gusting strong to extreme. Freezing level dropping to 1600 m.

Avalanche Summary

Several recent natural, small to large (size 1-2.5) wind slab avalanches were reported on northwest through northeast aspects at upper elevations on Monday.

On January 16th, a natural, size 2 wind slab stepped down to the deep persistent basal facets below a rock band, details here.

Snowpack Summary

Continuing west and southwest winds have formed stiff wind slabs on lee and cross-loaded terrain features at upper elevations. 

A crust can be found up to treeline and on solar aspects in the alpine due to previous warming and sun exposure. 

A well consolidated mid-pack overlies a generally weak basal snowpack. The bottom 10-20 cm of the snowpack consists of facets and deteriorating crusts. Although inherently weak, the benign weather pattern early this week likely promoted a decreasing trend in reactivity for this avalanche problem. Areas that are most likely to harbor this problem are shallow, rocky start zones. 

Terrain and Travel

  • Watch for wind-loaded pockets especially around ridgecrest and in extreme terrain.
  • Avoid steep, rocky, and wind effected areas where triggering slabs is more likely.

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.