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Archived

Avalanche Forecast

Dec 31st, 2019–Jan 1st, 2020
Alpine
4: High
The avalanche danger rating in the alpine will be high
Treeline
4: High
The avalanche danger rating at treeline will be high
Below Treeline
3: Considerable
The avalanche danger rating below treeline will be considerable
Alpine
4: High
The avalanche danger rating in the alpine will be high
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
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 Coastal.

Avoid avalanche terrain. Heavy snowfall and strong wind have resulted in dangerous avalanche conditions.

Confidence

Moderate - A small change in the upper snowpack could dramatically change avalanche conditions.

Weather Forecast

Tuesday night: 5-15 cm of snow with rain possible below 1000 m, light wind from the south, freezing level around 1200 m with alpine high temperatures around +1 C.

Wednesday: 15-20 cm of snow, strong wind from the west, freezing level drops to 500 m and alpine high temperatures drop to -5 C.

Thursday: Scattered flurries, light variable wind, alpine high temperatures around -8 C.

Friday: 5-10 cm of snow, moderate wind from the southeast, alpine high -8 C.

Avalanche Summary

Large natural avalanches up to size 3.5 have been reported in Bear Pass since the start of the storm. The natural storm slab avalanche cycle is likely still underway with ongoing new snow and wind at higher elevations. Below treeline, loose wet avalanches will be the main concern. 

Snowpack Summary

As of midday Tuesday, 45 mm of precipitation has fallen in 48 hours. This will have fallen as snow, up to 70 cm at high elevations in the north of the region, while rain soaked the snowpack below treeline. This has resulted in a mix of surface conditions with storm slabs, wind slabs, and wet loose avalanches occurring at different elevations. As the freezing level falls Wednesday, the snowpack will lock up where it was previously moist.

The recent loading has also added stress on the two layers of surface hoar buried 70-150 cm deep. Reports from the Shames area suggest buried surface hoar can be found on all aspects, but is more prevalent on southeast to southwest aspects around 800-1400 m.

Terrain and Travel

  • Avoid all avalanche terrain during periods of heavy loading from new snow and wind.
  • Avoid the runout zones of avalanche paths. Avalanches could run full path.
  • Storm slabs in motion may step down to deeper layers resulting in large avalanches.

Avalanche Problems

Storm Slabs

Heavy accumulations of new snow and strong wind have created large unstable slabs at upper elevations. Below treeline, the potential for avalanches will decrease through the day as freezing levels fall and lock up the previously moist snow.

Aspects: All aspects.

Elevations: All elevations.

Likelihood: Very Likely

Expected Size: 1 - 3

Persistent Slabs

New snow loads will stress weak layers of surface hoar buried 70-150 cm deep. This could result in large avalanches that propagate across terrain features and run far distances. The warm up/cool down temperature swing over the last few days may have destroyed this problematic layer below treeline.

Aspects: All aspects.

Elevations: All elevations.

Likelihood: Possible - Likely

Expected Size: 1 - 2