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

Regions

Kootenay Boundary.

Avalanche hazard will increase through the day Tuesday, likely peaking overnight. Avoid all avalanche terrain during periods of heavy snowfall and strong wind, and be aware of what is above you at all times.

Confidence

Moderate - We are confident the likelihood of avalanche will increase with the arrival of the forecast weather. Uncertainty is due to the limited number of field observations.

Weather Forecast

Yet another storm arrives Tuesday, becoming warmer (and wetter) on Wednesday before cooling as precip tapers on Thursday.

Monday night: Mostly cloudy. Southwest wind increasing to strong. Freezing level 1700m.

Tuesday: 15-25 cm new snow. Strong southwest wind. Freezing level 1800 m. 

Wednesday: 10-15 mm mixed precipitation. Strong southwest wind. Freezing level 2500 m.

Thursday: Flurries. Moderate westerly wind. Freezing level dropping 2000 to 1500 m.

Avalanche Summary

We've had no reports of avalanche activity over the weekend.

On Friday, minor avalanche cycle size 1-2 was observed on north facing alpine start zones. A size 1.5 skier accidental storm slab was reported on the Mountain Information Network near Nelson. They noted a fast moving avalanche with wide propagation, supported by a hard bed surface.

Note that there are very few field observations in the Kootenay Boundary this early in the season. Backcountry users need skills in assessing conditions and decision making. If you go out in the mountains, please share your observations and/or photos on the Mountain Information Network!

Snowpack Summary

15-25 cm of new snow falls over a moist upper snowpack. In the Okanagan a 2mm rain crust may exist in the upper snowpack, at the interface between recent storms.

The mid-November crust is down 30-60 cm and is up to 10 cm thick. The lower snowpack is a series of crust and facet layers. At the bottom of the snowpack, up to 20 cm of faceted snow may be found. 

Snowpack depths at treeline range from 50-100 cm, with alpine depths exceeding 150 cm in areas. Below 1700m, snowpack depths decrease rapidly.

Terrain and Travel

  • Avoid all avalanche terrain during periods of heavy loading from new snow, wind, or rain.
  • Avoid traveling through runout zones during stormy periods when large avalanches are likely.

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.