South Columbia Avalanche Forecast

Issued: Dec 28th, 2021 4:00PM

Wed Dec 29th Current Conditions
Alpine Moderate Treeline Moderate Below Treeline Moderate
Thu Dec 30th 2 Day Outlook
Alpine Moderate Treeline Moderate Below Treeline Moderate
Fri Dec 31st 3 Day Outlook
Alpine Moderate Treeline Moderate Below Treeline Moderate

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

The potential to trigger wind slabs and a buried weak layer are keeping the danger elevated.

Summary

Confidence

Moderate - Uncertainty is due to the fact that persistent slabs are particularly difficult to forecast.

Weather Forecast

TUESDAY NIGHT: Mostly cloudy with isolated snowfall, accumulation 1 cm, 15 km/h north wind, alpine temperature -23 C.

WEDNESDAY: Clear skies with no precipitation, 15 to 30 km/h west wind, alpine temperature -21 C.

THURSDAY: Cloudy with snowfall, accumulation 5 cm, 20 to 40 km/h southwest wind, alpine temperature -22 C.

FRIDAY: Mix of sun and cloud with no precipitation, 15 km/h north wind, alpine temperature -22 C.

Avalanche Summary

A few wind and storm slab avalanches were triggered naturally and by riders on Tuesday. They were generally small to large (size 1 to 2), on all aspects, and at treeline and alpine elevations.

There have been a few reports of activity on the early-December weak layer described in the Snowpack Summary, including two natural avalanches and one triggered by a rider. They were generally large (size 2 to 3), on all aspects, and between about 1700 m and up to 2600 m.

Similar avalanche activity is possible for Wednesday, given similar weather conditions and cold temperatures limiting bonding of the snowpack.

Snowpack Summary

Cold air continues to facet the top of the snowpack. The cold air also means that old wind slabs found on all aspects could linger. There is potential for new wind slabs to start forming on Wednesday afternoon as the wind speed increases.

A weak layer of feathery surface hoar may be found around 30 to 50 cm deep. It is most likely to be found in sheltered alpine features, around treeline, or open features below treeline. Although avalanche activity hasn't been prominent on this layer, it has been reactive in recent snowpack tests.

Sugary faceted grains may be found around the early-December melt-freeze crust 70 to 150 cm deep. The layer is most prevalent around 1700 m to 2400 m but could exist at lower and higher elevations for pockets of the region. This layer is spatially variable, with many areas showing good bonding to the crust whereas other areas showing concern. This layer has been most reactive where it remains shallower than about 100 cm. Learn more about how to manage this problem here.

Terrain and Travel

  • Recent wind has varied in direction so watch for wind slabs on all aspects.
  • Carefully evaluate steep lines for wind slabs.
  • Be careful with wind loaded pockets, especially near ridge crests and roll-overs.
  • Approach steep open slopes at and below treeline cautiously, buried surface hoar may exist.
  • Be aware of the potential for large avalanches due to the presence of a persistent slab.

Problems

Wind Slabs

An icon showing Wind Slabs

Likelihood

Possible

Expected Size

1 - 2

Wind slabs may remain reactive to human traffic in exposed terrain features. They may be found on all aspects due to varying wind directions.

Aspects:

All aspects.

Elevations:

Alpine, Treeline.

Persistent Slabs

An icon showing Persistent Slabs

Likelihood

Unlikely-Possible

Expected Size

2 - 3

We continue to receive sporadic reports of people triggering a weak layer of faceted grains around a melt-freeze crust that formed in early December. This layer is found around 70 to 150 cm deep and is most common at elevations between 1700 m and 2400 m.

Aspects:

All aspects.

Elevations:

All elevations.

Valid until: Dec 29th, 2021 4:00PM

Forecast Trend

The latest forecast danger ratings, broken down to elevation. See how an elevation is trending.