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Avalanche Forecast

Archived

Nov 26th, 2021–Nov 27th, 2021

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

Regions

Northwest Coastal.

Forecast new snow throughout the day on Saturday and extreme southwesterly winds will form fresh storm slabs reactive to human triggers. These slabs will be especially reactive on lee features at treeline and above.

Confidence

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

Weather Forecast

FRIDAY NIGHT: Cloudy with isolated flurries; 3-5 cm / Strong, southerly winds / Low of -7 / Freezing level 300 m.

SATURDAY: Snow/rain; 15-20 cm / Extreme, southwesterly winds / High of 0 / Freezing level rising to 1400 m.

SUNDAY: Snow/rain; 30-40 cm / Strong, southwesterly winds / High of 0 / Freezing level 1200 m

MONDAY: Mix of sun and cloud / Light, southwesterly winds / High of -6 / Freezing level surface.

Avalanche Summary

Large natural avalanches up to size 3 were reported on west and northwest aspects in the alpine on Thursday. 

Additionally, a size 3.5 natural wet slab avalanche was reported at around 1900 m that likely occurred on Wednesday.

Snowpack Summary

Southern portion of region (around Terrace):

A surface crust has likely capped the recent storm snow below around 1400 m. At higher elevations 30-60 cm of recent snow has been heavily wind affected by strong southwesterly winds, forming large wind slabs on lee features.

A prominent crust can be found near the bottom of the snowpack.

Treeline snowpack depths are estimated to be around 200-250 cm.

Northern region (around Bear Pass):

60-80 cm of recent snow has been heavily wind affected by strong southwesterly winds, forming large wind slabs on lee features at treeline and above.

Below the recent snow, two weak layers of surface hoar have been reported in sheltered areas, as well as a crust near the bottom of the snowpack.

Terrain and Travel

  • Give the new snow time to settle and stabilize before pushing into bigger terrain.
  • Watch for signs of instability like whumpfing, hollow sounds, shooting cracks or recent avalanches.
  • Be especially cautious as you transition into wind affected terrain.
  • Avoid freshly wind loaded terrain features.
  • Remember that the snowpack will be significantly different at higher elevations than lower down.

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.