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Archived

Avalanche Forecast

Dec 20th, 2019–Dec 21st, 2019
Alpine
2: Moderate
The avalanche danger rating in the alpine will be moderate
Treeline
2: Moderate
The avalanche danger rating at treeline will be moderate
Below Treeline
1: Low
The avalanche danger rating below treeline will be low
Alpine
2: Moderate
The avalanche danger rating in the alpine will be moderate
Treeline
2: Moderate
The avalanche danger rating at treeline will be moderate
Below Treeline
1: Low
The avalanche danger rating below treeline will be low
Alpine
2: Moderate
The avalanche danger rating in the alpine will be moderate
Treeline
2: Moderate
The avalanche danger rating at treeline will be moderate
Below Treeline
1: Low
The avalanche danger rating below treeline will be low

Regions: Northwest Inland.

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

Confidence

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

Weather Forecast

Friday Night: Cloudy with scattered flurries. Alpine temperature -5 C. South wind 20-40 km/hr.

Saturday: Cloudy with sunny periods. Alpine temperature -7 C. Southwest wind 15-20 km/hr.

Sunday: Mix of sun and cloud. Alpine temperature -7 C. Southwest wind 10-20 km/hr.

Monday: Cloudy with isolated flurries. Alpine temperature -8 C. south wind 20-30 km/hr. 

Avalanche Summary

There have been no recent reports of avalanche activity.

Between Tuesday and Wednesday, and further east of the Northwest Inland region, a natural wind slab avalanche cycle to size 2.5 in alpine and treeline areas was triggered by intense wind loading.

Snowpack Summary

15-30 cm of snow fell in the region early this week. Strong south-southwesterly winds have since developed reactive 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.

Avalanche Problems

Wind Slabs

Recent new snow has been redistributed by wind blowing from a variety of directions.

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood: Possible

Expected Size: 1 - 2