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

Regions

Northwest Inland.

Avoid all avalanche terrain as large avalanches are expected that may run to valley bottom with the arrival of this third atmospheric river.

Confidence

High - We are confident the likelihood of avalanche will increase with the arrival of the forecast weather.

Weather Forecast

Another atmospheric river has begun impacting the region with heavy precipitation of snow. By midday Tuesday, freezing levels will have climbed up and intense rain will have begun. No relief until later Wednesday. 

MONDAY NIGHT: Snow/rain; 10-15 cm/ Strong, southwesterly winds / Low of -8 / Freezing level around 500 m.

TUESDAY: Snow/rain; 20-30 cm / Southwesterly winds peaking at 100 km/h / High of -1 / Freezing level rising to 1500 m.

WEDNESDAY: Snow/rain; 5-10 cm / Strong, southwesterly winds / High of -6 / Freezing level around 1000 m.

THURSDAY: Cloudy with flurries 3-5 cm / Strong, southwesterly winds / High of -8 / Freezing level lowering to 300 m.

Avalanche Summary

Few natural avalanches (size 2) were reported recently in the alpine. With the incoming next wet warm storm, a large avalanche cycle is expected with many avalanches potentially running full.

Snowpack Summary

Recent new snow and previous wind have built wind slabs near ridgetops. These slabs will be especially deep on leeward features on north aspects. In specific alpine areas, wind slabs are sitting on a hard crust.

A crust formed in early November has been reported down 80-120 cm. There has been some evidence of large avalanches running on this crust. This will be a layer to monitor throughout the season.

Treeline snow depths are estimated to be 100-150 cm.

Terrain and Travel

  • Avoid all avalanche terrain during periods of heavy loading from new snow, wind, or rain.
  • Avoid traveling in runout zones. Avalanches have the potential to run to the valley floor.

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.