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Avalanche Forecast

Archived

Mar 14th, 2023–Mar 14th, 2023

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

Regions

Glacier.

A healthy snowfall at the Pass has reset the slopes, but the storm snow will take some time to properly bond to the underlying layers, especially where the snow landed on a crust.

Confidence

Moderate

Avalanche Summary

A natural avalanche cycle is underway (Monday afternoon) in the highway corridor as the snow falls and the temps rise. Numerous slides in the sz 2-3 range have been detected from most aspects.

Natural activity should subside quickly with dropping temps on Tues.

Snowpack Summary

Warm storm snow has fallen on a variety of surfaces (wind crust, sun crust, or surface hoar), accompanied by gusty SW winds. This storm slab is presently widespread through the region.

The generally strong snowpack sits on a deep persistent basal weakness of rounding facets/decomposing crust near the ground. Uncertainty surrounds this layer; each major snowfall has the potential to finally overload this weakness, resulting in large avalanches.

Weather Summary

The main thrust of moisture has passed the region, with unsettled weather Tues and general clearing/cooling Wed/Thurs.

Tonight: Flurries, trace snow, Alp low -14*C, mod/strong SW winds, freezing level (FZL) valley bottom

Tues: mix of cloud/sun, Alp high -10*C, light/mod S winds, 900m FZL

Wed: mix of sun/cloud, isolated flurries, Alp high -10*C, light/mod W winds, 900m FZL

Terrain and Travel Advice

  • Closely monitor how the new snow is bonding to the crust.
  • Avoid thin areas like rock outcroppings where you're most likely to trigger avalanches failing on deep weak layers.
  • Cornice failures could trigger very large and destructive avalanches.

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.