Avalanche forecast

Banff Yoho Kootenay

Feb 10 – 11, 2023Avalanche Canada
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Avalanche danger

Sun
Mon
Alpine
3 · Considerable
Treeline
3 · Considerable
Below
1 · Low
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Highlights

An avalanche cycle continues, evidenced by today's avalanche control results and observations of natural avalanches, We expect this current peak in avalanche danger to last for a few days while the snowpack adjusts. Human triggering is likely in avalanche starting zones.

Avalanche problems

  • Wind Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Likely - Very Likely
    Size
    1.5–3

    Sustained SW 40 km/hr winds with gusts to 75 km/hr Tuesday-Wednesday have moved significant amounts of new snow into leeward and cross-loaded areas. These slabs are sensitive and can be easily triggered by humans. Thursday they have become firmer and have pulled back into lower-angle terrain when releasing. Natural activity may subside over the next few days but remain very careful for human-triggered windslabs.

  • Deep Persistent Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Likely - Very Likely
    Size
    2–3.5

    The recent new snow and wind have added enough load to reawaken the deep persistent slab problem and we have observed several avalanches failing on the ground facets. Step back for a few days while the snowpack adjusts to this new load as we are likely to still see some unusual or large avalanches for the next few days.

Confidence

High

Avalanche Summary

Very touchy windslabs found Thursday during avalanche control on HWY 93 S. Some avalanches released when the bag hit the slope before the explosive detonated. Field teams observed widespread activity up to size 3 on the Icefields Parkway yesterday with propagations up to 300 meters and around the sunshine area Thursday to size 2. Avalanche control on Sunshine road Wednesday and on Hwy 93 S Thursday produced results up to size 3. Many avalanches stepped to the ground, especially in terrain that has not previously avalanched.

Snowpack Summary

Regional snowfall totals since Feb 1: Bow Summit 43 cm, Bosworth 37 cm, Sunshine 34 cm, Simpson 31 cm, Stanley 22 cm.

Strong winds have moved this new snow into widespread, reactive windslabs at higher elevations, confirmed by avalanche control on Wednesday & Thursday. Two crusts are buried within the upper snowpack and the November facets remain near the base. These buried weak layers are now producing avalanches, including a wake-up of the November facets. Minimal reactivity has been observed below treeline.

Weather Summary

Another system crosses the region Friday with 2-4 cm of snow, moderate-strong SW winds and alpine temperatures in the -2 to -10 range.

Saturday, expect isolated flurries with minimal accumulations. Winds will be in the 30-40 km/h range.

Sunday valley bottom temperatures reach +2C before dropping to cooler temperatures with the passage of a cold front bringing 5-10 cm and strong winds for areas along the Divide and West.

More details can be found in the Mountain Weather Forecast.

Terrain and Travel Advice

  • Make conservative terrain choices and avoid overhead hazard.
  • If triggered, wind slabs avalanches may step down to deeper layers resulting in larger avalanches.

Regions covered