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Avalanche Forecast

Dec 18th, 2016–Dec 19th, 2016
Alpine
3: Considerable
The avalanche danger rating in the alpine will be considerable
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
3: Considerable
The avalanche danger rating in the alpine will be considerable
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
3: Considerable
The avalanche danger rating in the alpine will be considerable
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: South Rockies.

New snow and strong winds on Monday will form new wind slabs in exposed terrain. Use extra caution in wind affected terrain and avoid freshly wind loaded features.

Confidence

Low - Timing, track, or intensity of incoming weather system is uncertain on Tuesday

Weather Forecast

Around 15 cm of snowfall is expected for Monday with strong alpine wind from the west and treeline temperatures around -10C. A break is expected Monday night before another pulse of precipitation arrives on Tuesday. Models are currently showing another 5-10 cm with strong alpine wind from the southwest and treeline temperatures around -5C. Dry and sunny conditions are currently forecast for Wednesday.

Avalanche Summary

On Friday and Saturday, ski cutting in the southeast of the region produced numerous size 1 wind slab avalanches in leeward terrain features. These were 5-15 cm thick. On Thursday, a natural size 2 wind slab occurred in the Corbin area. This occurred at 2000m elevation on a northeast aspect as a result of recently strong southwest winds. Check out the MIN post for more details and a photo. New snowfall and strong westerly winds are expected to result in new wind slab formation or add additional load to existing wind slabs which may still be lingering. Recent winds have mainly been from the southwest through northwest directions and wind slabs should be expected on opposite aspects in wind exposed terrain.

Snowpack Summary

The new snow buries a variable surface that developed over the last week of cold, dry, and windy conditions. This interface consists of scoured surfaces and wind slabs in wind exposed terrain, widespread faceting of the upper snowpack, and surface hoar up to 20 mm in sheltered areas. In sheltered areas, there may be a layer of surface hoar in the upper snowpack which was buried around December 10. The mid pack is generally well settled. The thick crust from mid-November is near the bottom of the snowpack and recent tests suggest that the crust is currently well bonded to the surrounding snow. Below treeline, the snowpack is very shallow and early season hazards such as stumps, rocks, and open creeks are still a major concern.

Avalanche Problems

Wind Slabs

New snowfall and strong winds are expected to form new wind slabs in exposed terrain on Monday. Older wind slabs may also still be lingering. The new snow buries a weak interface which may increase the reactivity of new slabs.
Use ridges or ribs to avoid pockets of wind loaded snow.Avoid slopes where the snow feels stiff or slabby.Avoid freshly wind loaded features.

Aspects: North, North East, East, South East, South.

Elevations: Alpine, Treeline.

Likelihood: Likely

Expected Size: 1 - 2