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Avalanche Forecast

Archived

Dec 5th, 2022–Dec 6th, 2022

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

Regions

Glacier.

The Nov 17th persistent weak layer (surface hoar/facets/crust) is well within the range of human triggering. Assess the snowpack carefully before stepping out into large open slopes, especially around treeline.

Dry, loose avalanches may pose a problem in steep, confined terrain if more snow (>10cm) falls than forecasted.

Confidence

Moderate

Avalanche Summary

On Sunday several sz 1-1.5 solar-induced loose dry avalanches occurred within the surface facet layer out of steep, rocky terrain. On Saturday Lone Pine produced a size 2 glide crack release which ran into the fan.

Whumpfing and remote-triggering continues on small, unsupported pillows below tree line on the Nov 17 persistent slab, both in GNP and adjacent to the region.

Snowpack Summary

Light fluff is falling onto a sugary, faceted surface. The Nov 17 persistent slab (surface hoar 5-30mm, facets, and crust) is down 50-80cm with the largest surface hoar present on sheltered slopes at treeline and below.

Snowpack depth is still variable (~120cm at treeline); early season hazards remain a concern.

Weather Summary

Cloud is spreading across the region, bringing 5-10cm of low-density snow and moderate West winds at ridgetop. Temps remain cool, with an Alp high of -13*C.

Continuing flurries, cool temps, and moderate SW winds prevail Wed/Thurs.

More details can be found in the Mountain Weather Forecast.

Terrain and Travel Advice

  • Carefully assess open slopes and convex rolls where buried surface hoar may be preserved.
  • Loose avalanches may start small but they can grow and push you into dangerous terrain.

Problems

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.

Loose Dry

Loose Dry avalanches are the release of dry unconsolidated snow and typically occur within layers of soft snow near the surface of the snowpack. These avalanches start at a point and entrain snow as they move downhill, forming a fan-shaped avalanche. Other names for loose-dry avalanches include point-release avalanches or sluffs.