Avalanche Forecast
Issued: Nov 26th, 2021 4:00PM
The alpine rating is , the treeline rating is , and the below treeline rating is Known problems include Storm Slabs.
wlewis,
Avalanche Canada
Cautiously approach avalanche terrain during the pause in this storm. Alpine and treeline elevations produced large natural avalanches Thursday. Careful route finding is still necessary with more reactive slabs found in wind effected terrain.
Summary
Confidence
Weather Forecast
FRIDAY NIGHT: 2-10cm of snow tapering throughout the day to flurries. Greater accumulation in the north. Freezing levels drop to valley bottom.
SATURDAY: A calm morning with light southwest winds gives way to an active pattern. 5-10cm of snow is expected over late afternoon with freezing levels at 1000m. The storm intensifies through the night as freezing levels rise above 2000m with 10-20cm of snow expected above, and mixed precipitation or rain below. Winds increase to strong southwest winds.
SUNDAY: Moderate to heavy precipitation throughout the day with freezing levels remaining elevated near 2000m. Strong west-southwest winds persist.
MONDAY: Winds decrease to moderate westerlies as the storm exits. Light accumulations are expected with clearing skies in the evening.
Avalanche Summary
On Thursday November 25th, numerous size 1.5 storm slab avalanches were skier triggered, failing on a mid storm weakness. Explosives produced several triggered storm slabs to size 1.5.
Nearby Glacier National Park observed a large natural storm slab avalanche cycle to size 3 on Thursday. This activity was widespread, on all aspects above 1800m. Explosives also produced avalanches up to size 3 in the same area, running full paths to valley bottom.
The North Columbia region reported numerous size 1.5-2 wind slab triggered remotely by machines at 1800m.
Snowpack Summary
New snow overnight will accumulate over recent wind effected storm snow. Storm totals reach 80cm in some areas and winds from the south and southwest have redistributed this into deeper pockets of denser snow over softer storm snow at alpine and treeline elevations.
The mid November crust is up to 5cm thick and found down 50-120cm on all aspects to 2350m, with faceting below the crust. The lower snowpack contains several early season crusts which appear well bonded with no recent reactivity.
Snowpack depths exceed 300cm at treeline and alpine elevations, while below 1600m depth decreases rapidly.
Terrain and Travel
- Expect slab conditions to change drastically as you move into wind exposed terrain.
- Approach lee and cross-loaded slopes with caution.
- Back off if you encounter whumpfing, hollow sounds, or shooting cracks.
- Continue to make conservative terrain choices while the storm snow settles and stabilizes.
Problems
Storm Slabs
Treeline and alpine elevations will be wind effected from the strong south-southwest winds, with deeper and more reactive slabs. Use caution at ridge crest, on cross-loaded slopes and mid slope terrain features. Human triggering remains likely as the snowpack will take time to gain strength from this significant new load.
Simple, low angle terrain that is free from overhead hazard is a good option throughout this ongoing active storm cycle.
Aspects: All aspects.
Elevations: All elevations.
Likelihood
Expected Size
Valid until: Nov 27th, 2021 4:00PM
