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Avalanche Forecast

Archived

Jan 24th, 2023–Jan 25th, 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

Glacier.

Wind slabs, on top of persistent slabs, on top of a deep persistent slab...this isn't a delicious layered cake from your local bakery.

This "house of cards" snowpack cannot be treated like a normal year. With so many lingering weaknesses, sticking to supported slopes with limited overhead exposure is paramount.

Confidence

Moderate

Avalanche Summary

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.

Crossover ran sz 2.5 onto its fan Tues morning.

Snowpack Summary

Reactive wind slabs are popping out at Tree-line and Alpine elevations, stepping down into the Jan 3 persistent weak layer.

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

Cloudy skies, gusty winds, flurries, and a slight warming Wed/Thurs summarize the weather picture.

Tonight: mainly cloudy, Alp low -8*C, moderate gusty W winds

Wed: mainly cloudy, isolated flurries, Alp high -4*C, 1500m FZL, moderate gusty W winds

Thurs: flurries, 5-10cm snow, Alp high -3*C, 1300m FZL, moderate gusty W 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.