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Avalanche Forecast

Archived

Apr 11th, 2023–Apr 12th, 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 unlikely, human triggered possible.
Treeline
Natural avalanches unlikely, human triggered possible.
Below Treeline
Natural avalanches unlikely, human triggered possible.

Regions

Glacier.

A warm, cohesive storm slab is perched atop either a crust on solar aspects, or surface hoar/facets on polar aspects.

With this knowledge, be aware of the possibility of remote triggering an avalanche onto yourself or others around you.

Confidence

Moderate

Avalanche Summary

Natural avalanche activity has decreased with the dropping temps. Monday's artillery control produced good results, with numerous avalanches from sz 2 to 4 propagating widely on the crust and/or the surface hoar/facet combo from March 31.

On Sunday, an experienced group remote-triggered an avalanche on a NE facing slope by the Cleaver, injuring 1 person.

Snowpack Summary

35cm of storm snow and strong, gusty SW winds have formed a reactive storm slab, thicker in lee features. This slab is propagating and stepping down to the March 31 layer (crust on solar aspects, facet/surface hoar on polar aspects).

The snowpack is generally strong. However, the Nov 17 basal weakness can still be found near the ground in many locations.

Weather Summary

Continuing unsettled weather for Wed, then a clearing trend for the end of the week.

Tonight: Isolated flurries, Alp low -9*C, moderate W winds, 700m FZL

Wed: Cloudy with some sun, Alp high -5*C, light NW winds, 1700m FZL

Thurs: Mix of sun and cloud, Alp high -5*C, light NW winds, 1700m FZL

Terrain and Travel Advice

  • Watch for signs of instability like whumpfing, hollow sounds, shooting cracks or recent avalanches.
  • Potential for wide propagation exists, fresh slabs may rest on surface hoar, facets and/or crust.
  • In areas where deep persistent slabs may exist, avoid shallow or variable depth snowpacks and unsupported terrain features.

Problems

Storm Slabs

Storm Slab avalanches are the release of a cohesive layer (a slab) of new snow that breaks within new snow or on the old snow surface. Storm-slabs typically last between a few hours and few days (following snowfall). Storm-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.

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.