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Avalanche Forecast

Archived

Jan 14th, 2023–Jan 15th, 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 unlikely, human triggered possible.
Below Treeline
Natural avalanches unlikely, human triggered possible.
Alpine
Natural avalanches possible, human triggered probable.
Treeline
Natural avalanches unlikely, human triggered possible.
Below Treeline
Natural avalanches unlikely.

Regions

Little Yoho.

With fresh wind loading in the alpine and another round of elevated winds with mild temperatures lined up for Sunday, slabs can be considered to be more sensitive to human triggering and natural avalanche activity to remain a possibility.

Confidence

Moderate

Avalanche Summary

Only a few loose dry avalanches to sz 1.5 were seen out the alpine on Mt Cascade today however teams only went as far as the Sunshine backcountry. Both ski hills reported dealing with fresh soft cornices that would trigger small slabs 5-10 wide and 10-20cm deep. Lake Louise triggered a sz 1.5 slab on the Dec 17 layer in a previously uncontrolled area that stepped down to the Nov 16 layer in a few pockets.

Snowpack Summary

10-20 cm of loose snow can be found on the surface including modest accumulations of new snow over the last few days at upper elevations. On Thursday and Friday, moderate to strong SW winds redistributed this loose snow in the alpine and formed fresh small, soft wind slabs in immediate lees with corresponding cornice development. Below 2000m warm temperatures have created moist snow: expect thin surface crusts as temperatures cool.

The December 17 persistent weak layer of facets is down 25-50 cm and continues to show failures with a sudden character in snowpack tests.

The November 16 deep persistent weak layer of facets and depth hoar is near the base of the snowpack (40 to 90cm deep) and continues to show failures with a sudden character in snowpack tests.

A profile from the Sunshine Backcountry today here.

Weather Summary

Freezing levels will return to valley bottom Saturday night after another warm day. Isolated flurries will end overnight to allow for broken skies to start Sunday. Freezing levels should just reach valley bottom Sunday as south winds increase to 30-40km/h. Clouds will increase in the afternoon and allow for trace amounts of snow to accumulate overnight as freezing levels return to valley bottom.

Terrain and Travel Advice

  • Uncertainty is best managed through conservative terrain choices at this time.
  • If triggered, wind slabs avalanches may step down to deeper layers resulting in larger avalanches.

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.

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.

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.