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Avalanche Forecast

Archived

Jan 30th, 2023–Jan 31st, 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 possible, human triggered probable.
Treeline
Natural avalanches unlikely, human triggered possible.
Below Treeline
Natural avalanches unlikely.

Regions

Glacier.

Fresh wind slabs may be forming with the bit of new snow and moderate Westerly winds overnight and into Tuesday. If triggered, these could step down to deeper layers, resulting in a large avalanche.

Confidence

Moderate

Avalanche Summary

No new natural or human-triggered avalanches were observed or reported on Monday.

Several human-triggered sz 1-1.5 avalanches were reported over the weekend on Avalanche Crest, Hermit Slide path, and Swiss Couloir.

A natural cornice failure triggered a size 3 deep persistent slab on the SE slope of Grizzly Peak on Saturday.

Snowpack Summary

Expect ~5cm of new snow by Tuesday morning. Recent variable winds have created new wind slabs in the alpine and down into tree line. Quality soft snow can be found in sheltered areas.

The early Jan surface hoar is buried 40-70cm and is most prevalent at tree line. The November 17th facet weakness can still be found near the base of the snowpack in many areas.

Weather Summary

Mainly cloudy with light snow on Tuesday with up to 5cm of snow accumulation. Temps gradually rise with an alpine high of -12. Ridgetop winds will be 20-30km/hr from the West.

Light snow and similar conditions for Wednesday.

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.