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Avalanche Forecast

Dec 20th, 2016–Dec 21st, 2016
Alpine
3: Considerable
The avalanche danger rating in the alpine will be considerable
Treeline
3: Considerable
The avalanche danger rating at treeline will be considerable
Below Treeline
2: Moderate
The avalanche danger rating below treeline will be moderate
Alpine
3: Considerable
The avalanche danger rating in the alpine will be considerable
Treeline
3: Considerable
The avalanche danger rating at treeline will be considerable
Below Treeline
2: Moderate
The avalanche danger rating below treeline will be moderate
Alpine
3: Considerable
The avalanche danger rating in the alpine will be considerable
Treeline
3: Considerable
The avalanche danger rating at treeline will be considerable
Below Treeline
2: Moderate
The avalanche danger rating below treeline will be moderate

Regions: Sea To Sky.

The last few days' new snow sits on a variety of potential weak sliding layers. As the storm snow settles in the coming days, it will be critical to evaluate the bond between new and old snow layers.

Confidence

Moderate - Timing, track, or intensity of incoming weather system is uncertain

Weather Forecast

Wednesday: Isolated flurries/ Moderate to strongsouthwest wind / Alpine temperature -5Thursday: Flurries, accumulation 5-10cm / Moderate southwest wind / Alpine temperature -5Friday: Cloudy with some sunny periods / Light to moderate north wind / Alpine temperature -6

Avalanche Summary

Recent reports indicate numerous explosive and a few skier triggered storm slab and wind slab avalanches to size 2 in the alpine and treeline at the storm snow/old snow interface. There were also reports of a few remotely triggered avalanches from thin wind scoured ridge crests into adjacent steeper loaded slopes. I would suspect there to be continued potential for skier and rider triggering with some recent very strong winds at upper elevations and a possible weak bond at the storm/old snow interface.

Snowpack Summary

30-50cm of new snow overlies the previous variable snow surface from last week, which includes hard wind pressed or scoured areas, old wind slabs, weak faceted snow, or surface hoar. Moderate to strong southwest wind has redistributed this new snow to form windslabs in the lee of terrain features in the alpine and treeline. The widespread mid-November crust is typically down 1-2m in the snowpack. Recent snowpack and explosive tests have shown the crust to be unreactive, but it could remain a problem in shallow alpine start zones.

Avalanche Problems

Storm Slabs

Recent new snow sits on top of a variety of potential weak sliding layers.
Avoid exposure to terrain traps where the consequences of a small avalanche could be serious.Dig down to find and test weak layers before committing to a line.

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood: Possible

Expected Size: 1 - 2

Wind Slabs

Recent strong southwest winds have created touchy wind slabs in the lee of terrain features
Be cautious as you transition into wind affected terrain.Use ridges or ribs to avoid pockets of wind loaded snow.

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

Elevations: Alpine, Treeline.

Likelihood: Possible - Likely

Expected Size: 1 - 3