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Avalanche Forecast

Archived

Nov 27th, 2022–Nov 28th, 2022

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 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.

Regions

Glacier.

An Arctic air mass approaches, bringing cold temps and light Northerly winds. The freshly formed wind slabs and the Nov 17 persistent slab remain sensitive to human triggering.

There are still many early-season hazards just below the snow surface. Bring extra warm layers and leave plenty of time to ski out in daylight at the end of your day.

Confidence

Moderate

Avalanche Summary

A natural, widespread avalanche cycle occurred early Sunday morning with numerous avalanches in the size 1.5-2.5 range and a few up to size 3.0

Natural avalanche activity is tapering off, but the persistent slab and new wind slabs will remain sensitive to human triggering.

Snowpack Summary

50cm of storm snow over the last few days accompanied by strong SW winds on Sunday has built fresh wind slabs. The Nov 17 persistent slab (surface hoar, facets, and crust) is down 60-80cm. The surface hoar (5-30mm) is largest at treeline and below.

The early season hazards are slowly being buried but still remain a concern. The height of snow at treeline is ~140cm.

Weather Summary

An Arctic airmass from the North will slide down into the region bringing cold temperatures, dry conditions, and a mix of sun and cloud on Monday. Alpine temps will range from -15 to -20.

Snow and warming temperatures are forecasted to return by Wednesday.

More details can be found in the Mountain Weather Forecast.

Terrain and Travel Advice

  • Watch for newly formed and reactive wind slabs as you transition into wind affected terrain.
  • Carefully assess open slopes and convex rolls where buried surface hoar may be preserved.
  • If triggered, wind slabs avalanches may step down to deeper layers resulting in larger avalanches.

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.