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Avalanche Forecast

Archived

Nov 25th, 2020–Nov 26th, 2020

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

Regions

Sea To Sky.

Welcome to the first forecast of the season! Wind slabs at higher elevation may be possible to trigger on Thursday.

Confidence

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

Weather Forecast

WEDNESDAY NIGHT: Partly cloudy, light northwest wind, alpine temperature -6 C.

THURSDAY: Increasing clouds with afternoon snowfall, accumulation 2 to 5 cm, light to moderate southwest wind, alpine temperature -5 C.

FRIDAY: Cloudy with snowfall, accumulation 15 to 25 cm, moderate to strong southwest wind, alpine temperature -3 C, freezing level 1400 m.

SATURDAY: Early-morning snowfall then clearing, accumulation 20 to 30 cm, moderate southwest wind, alpine temperature -5 C.

Avalanche Summary

Small slabs within the recent snow were triggered by explosives on Wednesday.

Our eyes and ears in the mountains are limited at this time of year and may continue this winter due to fewer professional observations. If you see anything while out in the field, please consider sharing it with us and fellow recreationists via the Mountain Information Network (MIN). Even just a photo of where you went is helpful. A big thank you to those that have already shared their observations thus far.

Snowpack Summary

The snowpack depth varies substantially with elevation. Around 30 to 70 cm should be expected below treeline, 80 to 100 cm near treeline, and around 150 cm may be found in the alpine.

Around 20 cm of snow fell across the region on Tuesday with strong to extreme southerly wind. This storm likely produced wind slabs in lee terrain features at higher elevations.

A melt-freeze crust found about 50 cm from the snow surface has been reported up to an elevation of at least 1800 m. Reports suggest that the snowpack is well-bonded to this crust. Another melt-freeze crust is found about 30 cm off the ground surface, which may have a thin layer of weak and sugary faceted grains above it. There also may be a thin layer of feathery surface hoar crystals found above the crust, particularly in sheltered terrain features at and above treeline. There is uncertainty as to whether these layer will be a concern going forward.

Terrain and Travel

  • Watch for newly formed and reactive wind slabs as you transition into wind affected terrain.
  • Be alert to conditions that change with aspect and elevation.
  • Use small low consequence slopes to test the bond of the new snow.
  • Be cautious of buried obstacles especially below treeline.

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.