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Archived

Avalanche Forecast

Dec 3rd, 2021–Dec 4th, 2021
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
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 Coastal.

Remain cautious with terrain choices as the snow settles from an epic series of storms. Wind loaded features are the most likely to produce large avalanches.

Confidence

Moderate - We are confident about the possible sizes of avalanches, should one release; what is less certain is the likelihood of triggering.

Weather Forecast

Stormy weather lingers for one more night. Freezing levels remain mostly at valley bottom.

Friday Night: Mostly overcast. 5-15 cm new snow. Strong southwest wind. Alpine temperature around -13 C. Freezing level up to 250m.

Saturday: Partly Cloudy. Possible trace of new snow. Moderate northwest wind. Alpine temperature around -15 C.

Sunday: Mostly cloudy by the afternoon. No new snow expected. Moderate northwest wind. Alpine temperature around -15 C.

Monday: Clear morning, cloudy afternoon. No new snow expected. Moderate southwest wind. Alpine temperature above -10 C with possible temperature inversion. 

Avalanche Summary

The few avalanches reported on Thursday in the south of the region seemed to only move the recent storm snow.

 

On Wednesday morning, a few small natural avalanches were observed and explosive and machine control work produced size 1-2 storm slab avalanches.

Near Stewart, there is evidence that a widespread avalanche cycle occurred during the past storm, up to size 3 in wind loaded terrain at treeline and in the alpine. 

Snowpack Summary

30-60 cm of snow in the last 48 hours continues to be redistributed and built into slabs by moderate to strong winds. 

The previous wet storm produced a new crust that was buried Nov 30 or Dec 1. This crust exists up to 2000 m in the southwest of the region, and may only be found up to 1200 m in areas east of Terrace. Expect slab avalanches to propagate more easily on this crust and run far.

At higher elevations where this crust is not present, the storm snow overlies old wind slab or wind stripped ridge tops.

Treeline snowpack depths are estimated to be around 2-3 m, and a prominent crust can be found near the base of the snowpack.

Terrain and Travel

  • Be alert to conditions that change with elevation and wind exposure.
  • Avoid lee and cross-loaded slopes at and above treeline.
  • Keep in mind the crust offers an excellent bed surface for avalanches.

Avalanche Problems

Storm Slabs

New snow has us watching for storm slabs at all elevations, but don't forget that in the last week, strong to extreme winds formed thick wind slabs in lee terrain features and cross-loaded slopes at upper elevations. 

An avalanche in the storm snow may trigger a deeper wind slab underneath. Slabs may be especially reactive where they sit on top of a slick crust.

Aspects: All aspects.

Elevations: All elevations.

Likelihood: Possible - Likely

Expected Size: 2 - 3