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Avalanche Forecast

Archived

Jan 25th, 2023–Jan 26th, 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 unlikely, human triggered possible.
Below Treeline
Natural avalanches unlikely, human triggered possible.

Regions

Glacier.

Watch for fresh wind slabs forming Thursday with new snow and winds forecast. These could be touchy to rider triggering.

Use caution in shallow, rocky areas for triggering a weak layer at the base of the snowpack.

Confidence

Moderate

Avalanche Summary

On Wednesday we observed several natural avalanches, size 2-2.5 along the highway corridor in south facing terrain. Likely triggered by wind loading and sun effect midday.

Backcountry reports, also on Wednesday, of rider triggering soft slabs, up to size 1, down 30-40cm on a sun crust. And sluffing in steep terrain.

A field team on Connaught/Lookout triggered a sz 1 wind slab on Monday, which stepped down to the Jan 3 surface hoar. They also observed several sz 1 loose/dry avalanches on the N Face of MacDonald, running in extreme terrain.

Cheops North 4 ran sz 2 Monday morning, while Frequent Flyer ran sz 2 on Sat into the creek.

Near neighbours have reported large natural and rider triggered avalanches up to sz 3, both wind slabs and deep persistent slabs. See MIN's for details.

Snowpack Summary

Reactive wind slabs are popping out at Treeline and Alpine elevations, stepping down into the Jan 3 persistent weak layer. Thin sun crust down 30-40cm. Good skiing below treeline with small amounts of unconsolidated storm snow keeping the surface soft.

The mid-pack facets are slowly rounding and gaining strength, while the basal facets and Nov 17 facet/SH/crust weakness are still reactive when isolated in snowpack tests.

Weather Summary

Unsettled weather Thurs/Fri with flurries bringing light/moderate snowfall and light/mod W/NW winds.

Tonight: Cloudy w/flurries, 2 cm, Snow level 800m lowering to valley bottom this evening, Moderate W winds.

Thurs: Cloudy w/flurries, Alp high -4*C, 1500m FZL, moderate gusty W winds

Fri: flurries, 5-10cm snow, Alp high -6*C, 1200m FZL, moderate gusty N winds

Terrain and Travel Advice

  • Watch for newly formed and reactive wind slabs as you transition into wind affected terrain.
  • Carefully assess open slopes and convex rolls where buried surface hoar may be preserved.
  • Avoid thin areas like rock outcroppings where you're most likely to trigger avalanches failing on deep weak layers.

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.