Avalanche Forecast

Issued: Dec 5th, 2021 4:00PM

The alpine rating is moderate, the treeline rating is moderate, and the below treeline rating is low. Known problems include Wind Slabs and Deep Persistent Slabs.

Avalanche Canada bchristie, Avalanche Canada

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Choose terrain sheltered from the wind, and avoid thin, rocky start zones. Right now, wind slabs are the common problem, but triggering a high consequence, deep slab avalanche is possible. 

Summary

Confidence

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

Weather Forecast

Sunday Night: Mostly cloudy. Possible trace of snow. Light west wind. Alpine temperature around -13 C.

Monday: Mostly clear. No new snow expected. Light northeast wind, becoming moderate southwest by the evening. Alpine temperature above -10 C with a possible temperature inversion

Tuesday: Overcast. 10-30 cm snow expected. Extreme southwest winds. Freezing level rising to 250 m. Alpine temperature around -5 with a possible temperature inversion.

Wednesday: Mostly cloudy. 5-20 cm snow expected. Strong west winds. Freezing level dropping back to valley bottom with alpine temperatures around -10 C.

Avalanche Summary

With some improved visibility, observations of avalanches that occured during the last storm are starting to trickle in. 

Natural, explosive, and cornice triggered slab avalanches have been reported up to size 3.

Some very large explosive triggered avalanches were reported in Bear Pass, having us thinking about the potential for a deep persistent weak layer.

Snowpack Summary

There are recent reports of large to very large avalanches running on or near the ground in the Bear Pass area and around Smithers. We don't know how widespread this problem may be, or if both events even reflect the same avalanche problem, but we are definitely keeping an eye on it, and would be avoiding large features and areas with thin to thick snowpack transitions for now. 

Due to recent, variable winds, you may find wind slabs on many aspects, and on both sides of ridges. Some exposed areas may be stripped back to the Nov 30/Dec 1 Crust. 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.

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

  • Avoid lee and cross-loaded slopes at and above treeline.
  • Keep in mind the crust offers an excellent bed surface for avalanches.
  • Avoid thin areas like rock outcroppings where you're most likely to trigger avalanches failing on deep weak layers.

Problems

Wind Slabs

An icon showing Wind Slabs

Yesterday's forecaster blog does a great job of capturing the challenging travel and decision-making we'll likely encounter in the backcountry right now. 

Slabs may be especially reactive where they sit on top of a slick crust.

Watch for wind loading on all aspects due to recent variable wind directions.

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Possible

Expected Size

2 - 3

Deep Persistent Slabs

An icon showing Deep Persistent Slabs

Avoid large features, and thin rocky start zones. Information is still being gathered about this potential weak layer near the bottom of the snowpack. 

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Unlikely

Expected Size

2.5 - 4.5

Valid until: Dec 6th, 2021 4:00PM