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Avalanche Forecast

Archived

Jan 28th, 2023–Jan 29th, 2023

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

Regions

Glacier.

Buried surface hoar layers from early January remain at an ideal depth for rider triggering. Traffic may have reduced the reactivity of this weakness on our more popular runs, but approach terrain that is off the beaten path with extra caution.

Cold temperatures are adding to the risks of backcountry travel, bring extra layers and leave yourself a little extra buffer to get out safely at the end of the day.

Confidence

High

Avalanche Summary

On Saturday, there was a large (size 3) cornice triggered deep slab avalanche from the South East slopes of Grizzly peak. Strong Northerly winds are the suspected trigger. There was also a small (size 1) skier triggered avalanche on a steep roll mid-way down Avalanche crest.

Artillery control on Friday produced numerous size 2-2.5, and a few size 3, slab avalanches in the Alpine and at Treeline. These are suspected to have been primarily windslabs, with some propagating more widely, suggesting failure on the early January surface hoar. These avalanches started as fast moving powder clouds, but quickly ground to a halt when they hit the refrozen snow mid-track (~1700m).

On Wednesday, a Skier triggered an avalanche on McGill shoulder,the failure plane for this was suspected to be an early January surface hoar layer down 50cm.

Snowpack Summary

Watch for fresh wind slabs in strange places from outflow (Northerly) winds. There were also previous wind slabs at upper elevations from strong SW winds.

Warm temps this week have left a surface crust below ~1700m, and a buried sun/temperature crust (Jan 21st) on steep south facing terrain, down 30-40cm around treeline.

The early January Surface Hoar layers (Jan 3rd and 12th), are buried down 40-70cm, and most likely to be rider triggered at treeline.

Large facetted crystals and the November 17th facet/SH/crust weakness can still be found near the base of the snowpack in many areas.

Weather Summary

The arctic ridge of high pressure will remain over our area until late Monday.

Tonight: Mostly clear, Alpine Low -21*C, Light NE ridgetop winds.

Sunday: Mostly Sunny. Alpine High -18*C. Light NW winds.

Monday: Cloudy periods, isolated flurries. Low -18*C, High - 15*C. Light W wind.

Tuesday: Cloudy with isolated flurries. Low -15*C, High -12*C. Light SW wind.

Terrain and Travel Advice

  • Be careful with wind slabs, especially in steep, unsupported and/or convex terrain features.
  • Carefully assess open slopes and convex rolls where buried surface hoar may be preserved.

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.