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Avalanche Forecast

Archived

Jan 6th, 2023–Jan 7th, 2023

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

Regions

Little Yoho.

Forecasters remain very concerned about the potential for human triggering. The deep persistent slab problem in particular has shown its potential for long propagation and remote triggering. Keep the slope angle mellow and the slope size small.

Confidence

Moderate

Avalanche Summary

Sunshine Village reported a few natural size 2 slabs on nearby Mt Brett. Jasper national park reported a sz 2.5 running to valley bottom off of Mt Kitchener

Snowpack Summary

10-20cm of soft surface snow sits over a generally weak midpack. The December 17 surface hoar and facet persistent layer is down 25-60cm. The November 16th and November 25 deep persistent layers of facets, depth hoar, and/or crusts are found near the base of the snowpack. Both of these problem layers show moderate to hard snowpack test scores of a sudden character.

Weather Summary

Friday night SW winds 40-50km/h will continue in the alpine with a low of -15C at treeline. Saturday will see a high of -5-10C at treeline with alpine winds diminishing in the PM to 20-30kmk/h. Saturday night will see a low of -12C. Trace amounts of snow and mainly cloudy skies closer to the divide through the period.

Terrain and Travel Advice

  • Uncertainty is best managed through conservative terrain choices at this time.
  • Use careful route-finding and stick to moderate slope angles with low consequences.

Problems

Deep Persistent Slabs

Deep Persistent Slab avalanches are the release of a thick cohesive layer of hard snow (a slab), when the bond breaks between the slab and an underlying persistent weak layer deep in the snowpack. The most common persistent weak layers involved in deep, persistent slabs are depth hoar or facets surrounding a deeply buried crust. Deep Persistent Slabs are typically hard to trigger, are very destructive and dangerous due to the large mass of snow involved, and can persist for months once developed. They are often triggered from areas where the snow is shallow and weak, and are particularly difficult to forecast for and manage.

Persistent Slabs

Persistent Slab avalanches are the release of a cohesive layer of snow (a slab) in the middle to upper snowpack, when the bond to an underlying persistent weak layer breaks. Persistent layers include: surface hoar, depth hoar, near-surface facets, or faceted snow. Persistent weak layers can continue to produce avalanches for days, weeks or even months, making them especially dangerous and tricky. As additional snow and wind events build a thicker slab on top of the persistent weak layer, this avalanche problem may develop into a Deep Persistent Slab.