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Avalanche Forecast

Archived

Dec 9th, 2021–Dec 10th, 2021

Alpine
Natural avalanches unlikely, human triggered possible.
Treeline
Natural avalanches unlikely, human triggered possible.
Below Treeline
Natural avalanches unlikely.
Alpine
Natural and human triggered avalanches likely.
Treeline
Natural avalanches possible, human triggered probable.
Below Treeline
Natural avalanches unlikely, human triggered possible.
Alpine
Natural avalanches possible, human triggered probable.
Treeline
Natural avalanches unlikely, human triggered possible.
Below Treeline
Natural avalanches unlikely, human triggered possible.

Regions

South Columbia.

Pay close attention to changing conditions as avalanches will become more likely with the incoming storm.

Confidence

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

Weather Forecast

A frontal system will arrive on Friday night and bring strong wind and new snow.

THURSDAY NIGHT: Mostly cloudy skies, no significant precipitation, light to moderate wind from the west, treeline temperatures drop to -10 C.

FRIDAY: Increasing cloud with afternoon flurries bringing up to 5 cm of snow, strong wind from the southwest with gusts to 60 km/h, treeline temperatures increase to -7 C.

SATURDAY: Snowing throughout the day with a total of 10-25 cm, strong wind from the southwest with gusts to 90 km/h, treeline temperatures around -5 C.

SUNDAY: Partly cloudy with scattered flurries and up to 5 cm of new snow, moderate wind from the southwest, treeline temperatures around -8 C.

Avalanche Summary

Reports from Wednesday highlight that slabs are becoming more reactive. There were several reports of natural size 2 avalanches in alpine terrain as well as several human triggered size 1 wind slabs around treeline. The most reactive slabs were on convex wind-affected slopes. Most avalanches were in the top 20-30 cm of snow.

We will likely see more widespread avalanche activity in all types of terrain with the incoming storm this weekend, but on Friday, the most likely avalanche activity will continue to be in wind-affected areas.

Snowpack Summary

20-40 cm of recent snow will begin settling above a variety of suspect layers over the next few days. The most widespread layer is a crust beneath this snow that formed during last week's atmospheric river. This crust extends into the alpine (as high as 2400 m), and there is potential for a poor bond to this crust. There is also a thin breakable crust closer to the surface. We are uncertain about how reactive the recent snow will be as it settles over the upcoming days. 

The snowpack structure is relatively simple beneath the crust, with treeline snow depths around 100-200 cm.

Terrain and Travel

  • Be carefull around freshly wind loaded features.
  • Avoid areas where the snow feels stiff and/or slabby.
  • Closely monitor how the new snow is bonding to the crust.
  • Be alert to conditions that change with elevation and wind exposure.

Problems

Wind Slabs

Wind Slab avalanches are the release of a cohesive layer of snow (a slab) formed by the wind. Wind typically transports snow from the upwind sides of terrain features and deposits snow on the downwind side. Wind slabs are often smooth and rounded and sometimes sound hollow, and can range from soft to hard. Wind slabs that form over a persistent weak layer (surface hoar, depth hoar, or near-surface facets) may be termed Persistent Slabs or may develop into Persistent Slabs.