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Avalanche Forecast

Archived

Dec 14th, 2023–Dec 15th, 2023

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

Regions

Glacier.

A weak layer is present at the ideal depth for large rider triggered avalanches.

The safest way to manage this problem is through conservative terrain choices.

Confidence

Moderate

Avalanche Summary

No new natural avalanches were observed along the highway corridor.

On Tuesday, a group triggered a size 2.5 on Ursus Minor. This avalanche was triggered in a wind loaded pocket near ridge top, in a generally shallow faceted snowpack. Wide, impressive propagation occurred on the Dec 1 surface hoar, facet layer.

Snowpack Summary

Storm snow buries a new surface hoar layer, which sits on top a thin sun crust in steep terrain.

A rain crust down 40cm is present up to 2100m.

A weak layer (Dec 1 surface hoar) buried 70-100cm deep continues to produce 'sudden' results in snowpack tests and human triggered avalanches. The surface hoar sits on a sun crust on solar aspects at upper elevations.

The base of the snowpack is facetted at upper elevations.

Weather Summary

Friday: Trace precip, moderate SW winds, High: -3 °C, Freezing level 1500m.

Saturday: Cloudy, sunny periods, High: -3 °C, Moderate SW winds, freezing level 1400m.

Sunday: Cloudy, sunny periods, High: -1°C, light SW winds, freezing level 1700m.

Terrain and Travel Advice

  • Avoid steep, rocky, and wind effected areas where triggering slabs is more likely.
  • Potential for wide propagation exists, fresh slabs may rest on surface hoar, facets and/or crust.

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.

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.