Avalanche Forecast

Issued: Nov 26th, 2021 4:00PM

The alpine rating is moderate, the treeline rating is moderate, and the below treeline rating is low. Known problems include Storm Slabs.

Avalanche Canada wlewis, Avalanche Canada

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Investigate the bond between recent storm snow and the snowpack during the pause in this storm. More reactive slabs will be found in wind effected terrain features at treeline and above. Avalanche danger will increase again with another warm and wet storm Saturday night. 

Summary

Confidence

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

Weather Forecast

FRIDAY NIGHT: Chance of flurries with moderate westerlies. Freezing levels drop to valley bottom overnight. 

SATURDAY: A calm start with light southwest winds, freezing levels remain below 1400m. Another front brings windy and wet weather to the region in the evening. 10-25mm is expected overnight. Snow will become mixed precipitation and rain as freezing levels rise throughout the night, reaching 2500m by early Sunday morning. Winds increase to strong southwest winds as the storm progresses.

SUNDAY: Up to 10mm throughout the day with freezing levels remaining above 2000m. Strong southwest winds persist.

MONDAY: Winds shift to the moderate westerlies with light accumulations as the storm exits. Skies begin to clear in the evening.

Avalanche Summary

Yesterday, 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.

On Wednesday, November 24th, multiple size 2.5 wind slabs were triggered by explosives in the Okanagan. These were reported on wind loaded east and southeast aspects up to 60cm deep.

Note that there are few field observations this early in the season. 

Snowpack Summary

Up to 15cm of storm snow received Thursday sits over a settling snowpack. In the Okanagan a 2mm breakable rain crust caps the storm snow.

The mid-November crust is down 25-50 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 40-100 cm, with alpine depths exceeding 150 cm in areas. Below 1700 m, snowpack depths decrease rapidly.

 

Terrain and Travel

  • Be alert to conditions that change with elevation and wind exposure.
  • Be careful with wind loaded pockets, especially near ridge crests and roll-overs.
  • Investigate the bond of the recent snow before committing to your line.

Problems

Storm Slabs

An icon showing Storm Slabs

Storm snow needs time to gain strength and bond with the snowpack. Step in to terrain cautiously and assess conditions as you travel, especially at treeline and alpine elevations. 

The most reactive deposits will be around ridgelines and in wind loaded terrain features.

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Possible - Likely

Expected Size

1 - 2

Valid until: Nov 27th, 2021 4:00PM

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