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Avalanche Forecast

Archived

Dec 21st, 2019–Dec 22nd, 2019

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, human triggered possible.
Below Treeline
Natural avalanches unlikely.

Regions

Northwest Inland.

Recent snow and wind has promoted wind slab development at upper elevations.

Confidence

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

Weather Forecast

Saturday: Cloudy with clear breaks. Alpine temperature -7 C. Light southwest wind.

Sunday: Mix of sun and cloud. Alpine temperature -7 C. Light southwest wind.

Monday: Cloudy with isolated flurries. Alpine temperature -6 C. Moderate southwest wind.

Tuesday: Cloudy with isolated flurries. Alpine temperature -5 C. Moderate south wind.

Avalanche Summary

There have been no recent reports of avalanche activity.

Snowpack Summary

15-30 cm of snow fell in the region early last week. Moderate south-southwesterly winds have since developed wind slabs, especially around ridge features and into the alpine.

Reports suggest there are 2 buried layers of surface hoar in the upper snowpack - one down 15-25 cm below the new snow, and another down 25-40. Where wind has scoured the snowpack, a crust from November is at or near the surface. In leeward terrain, a this crust is 40-60 cm deep, and may include surface hoar in sheltered openings up to treeline.

Older crusts can be found deeper in the snowpack and are generally breaking down. In areas with a relatively thin snowpack, the base of the snowpack likely consists of weak faceted grains.

Terrain and Travel

  • Watch for newly formed and reactive wind slabs as you transition into wind affected terrain.
  • Carefully assess open slopes and convex rolls where buried surface hoar may be preserved.

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.