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Avalanche Forecast

Archived

Nov 29th, 2021–Nov 30th, 2021

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

Regions

South Columbia.

Avalanche hazard will increase through the day Tuesday. Avoid all avalanche terrain during periods of heavy snowfall and strong wind. Be aware of what is above you at all times as large avalanches may run full path.

Confidence

Moderate - We are confident the likelihood of avalanche will increase with the arrival of the forecast weather. Uncertainty is due to the timing of the incoming weather system.

Weather Forecast

Yet another storm arrives Tuesday, becoming warmer (and wetter) on Wednesday before cooling as precip tapers on Thursday.

Monday night: Flurries starting, 5-10 cm. Moderate southwest wind. Freezing level 1600m.

Tuesday: 10-20 cm new snow. Moderate southwest wind increasing to strong overnight. Freezing level climbing to 1800 m. 

Wednesday: 10-20 mm mixed precipitation. Strong southwest wind. Freezing level 2300 m in the early am, dropping to 2100 m.

Thursday: Flurries tapering, up to 5 cm. Light westerly wind. Freezing level 1400 m.

Avalanche Summary

On Sunday, a widespread natural storm slab avalanche cycle was observed up to size 3 and running to valley bottom along the Highway 1 corridor near Revelstoke. Explosive control work at alpine and treeline elevations produced storm slabs up to size 2.5, some notables entraining loose wet and running full path.

On Friday, a natural storm slab avalanche cycle was observed size 2-3. Multiple size 1 and 1.5 avalanches were triggered by explosives and skiers near Revelstoke. The Mountain Information Network received several reports of reactive storm snow. Whumpfing and cracking within the storm snow was seen on low and steep angle terrain, at treeline and above. By Saturday, avalanche activity had largely subsided, the only reports being a few small skier controlled soft slabs on convex rolls.

Snowpack Summary

The snowpack hasn't had a lot of time to adjust to significant loading by recent storms, and yet another meteorological pounding arrives Tuesday. 15-30 cm of new snow falls amid strong wind, ontop of nearly a meter of recent moist snow. In some areas a rain crust may exist at the interface between recent storms.

The mid November crust is up to 5cm thick and found down 70-150cm with faceting below the crust. The lower snowpack contains several early season crusts which appear well bonded.

Snowpack depths exceed 300cm at treeline and alpine elevations, while below 1600m depth decreases rapidly with elevation. 

Terrain and Travel

  • Avoid all avalanche terrain during periods of heavy loading from new snow, wind, or rain.
  • Avoid exposure to overhead avalanche terrain, avalanches may run surprisingly far.

Problems

Storm Slabs

Storm Slab avalanches are the release of a cohesive layer (a slab) of new snow that breaks within new snow or on the old snow surface. Storm-slabs typically last between a few hours and few days (following snowfall). Storm-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.