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Avalanche Forecast

Archived

Nov 25th, 2021–Nov 26th, 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 unlikely, human triggered possible.
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.

New snow and strong southerly winds have created 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

THURSDAY NIGHT: Clearing with isolated flurries; 3-5 cm. / Strong, southwesterly winds / Low of -10 / Freezing level surface.

FRIDAY: Mix of sun and cloud / Strong, southwesterly winds / High of -5 / Freezing surface.

SATURDAY: Mostly cloudy with isolated flurries; 3-5 cm / Strong, southwesterly winds / High of -3 / Freezing level 500 m.

SUNDAY: Cloudy with isolated flurries; 0-3 cm / Strong, southwesterly winds / High of -3 / Freezing level 500 m.

Avalanche Summary

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

These recently formed storm slabs are expected to remain reactive to human triggers, especially on lee features at treeline and above.

Snowpack Summary

15-25 cm of recent snow and strong southerly winds have created fresh storm slabs reactive to human triggers at treeline and above.

Snowpack depths are above average for this time of year, with treeline depths averaging between 100-150 cm. The overall snowpack structure consists of settling storm snow above an early November crust that is now roughly 80-120 cm deep. There has been some evidence of large avalanche running on this crust, but it does not appear to be a major problem at this time. 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.