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

Regions

Northwest Inland.

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: Clearing skies / Strong, southwesterly winds / Low of -10 / Freezing level surface.

SATURDAY: Snow/rain; 10-20 cm / Extreme, southwesterly winds / High of -2 / Freezing level rising to 1300 m.

SUNDAY: Snow/rain; 10-20 cm / Strong, southwesterly winds / High of -1 / Freezing level 1000 m

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

Avalanche Summary

Several large, natural storm slab avalanches up to size 3 were reported on west and northwest aspects in the alpine on Thursday. 

Snowpack Summary

20-30 cm of recent snow at upper elevations and strong southerly winds have created fresh storm slabs reactive to human triggers.

At treeline and below, the snow was likely moist and has formed a surface 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.

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.