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Avalanche Forecast

Archived

Nov 28th, 2021–Nov 29th, 2021

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

Regions

Northwest Inland.

Wind slabs will be reactive at upper elevations. Given how uncertain conditions are, avoid big terrain at this time.

Confidence

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

Weather Forecast

Precipitation will ease further Sunday night. A brief break is expected Monday before snowfalls intensify rapidly with the approach of the next intense storm Tuesday and Wednesday.

SUNDAY NIGHT: Cloudy / Strong southwesterly winds / Low of -10 / Freezing level lowering to 300 m.

MONDAY: Cloudy with flurries 3-5 cm / Moderate, southwesterly winds / High of -8 / Freezing level around 300 m.

TUESDAY: Snow/rain; 15-30 cm / Extreme, southwesterly winds / High of -1 / Freezing level rising to 1500 m.

WEDNESDAY: Snow/rain; 10-15 cm / Strong, southwesterly winds / High of -5 / Freezing level rising to 1000 m.

Avalanche Summary

No new avalanches were observed in the last 24h due to poor visibility, despite the significant snowfalls and extreme wind at upper elevations. If you go out in the mountains, please post your observations and/or photos to the Mountain Information Network! 

Snowpack Summary

15-25 cm of new snow and strong southwesterly winds have formed reactive slabs sitting on a hard crust. Warmer temperatures are rapidly settling the storm snow, but strong winds continued to develop wind slabs near ridge tops. These slabs will be especially deep on leeward features on north aspects.

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

  • Remember that the snowpack will be significantly different at higher elevations than lower down.
  • Watch for newly formed and reactive wind slabs as you transition into wind affected terrain.
  • Make observations and assess conditions continually as you travel.

Problems

Wind Slabs

Wind Slab avalanches are the release of a cohesive layer of snow (a slab) formed by the wind. Wind typically transports snow from the upwind sides of terrain features and deposits snow on the downwind side. Wind slabs are often smooth and rounded and sometimes sound hollow, and can range from soft to hard. Wind 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.