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Avalanche Forecast

Archived

Dec 24th, 2019–Dec 25th, 2019

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

Regions

Northwest Inland.

Recent snow, continued flurries, and wind continue to promote slab development at upper elevations.

Confidence

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

Weather Forecast

Tuesday Night: Cloudy with isolated flurries, trace to 5 cm. Alpine temperature -6 C. West wind, 25-45 km/hr.

Wednesday: Mostly cloudy. Alpine temperature -7 C. Southwest wind, 30-50 km/hr.

Thursday: Snow and flurries, 10-25 cm. Alpine temperature -5 C. Southwest wind, 50-85 km/hr. Freezing level rising to 800 m.

Friday: Sun, cloud, and isolated flurries, 5-15 cm. Alpine temperature -6 C. Southwest wind, 15-30 km/hr gusting to 85 km/hr. Freezing level 1200 m.

Avalanche Summary

There have been no recent reports of avalanche activity.

Snowpack Summary

Flurries continue to add to 15-30 cm of snow from early last week. Moderate south-southwesterly winds continue to redistribute loose snow, and have developed wind slabs 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, this crust is 40-80 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.
  • Make observations and assess conditions continually as you travel.
  • 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.