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Avalanche Forecast

Archived

Dec 16th, 2024–Dec 17th, 2024

Alpine
Natural avalanches unlikely, human triggered possible.
Treeline
Natural avalanches unlikely, human triggered possible.
Below Treeline
Natural avalanches unlikely.
Alpine
Natural and human triggered avalanches likely.
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.

Regions

Glacier.

A dusting of fresh snow on Monday may make it difficult to visually identify recently formed wind slabs.

Investigate wind slab development on representative slopes before committing to large terrain features.

Confidence

Moderate

Avalanche Summary

Natural avalanche activity tapered off on Monday.

Several Size 1-2.5 natural wind slab avalanches were observed over the weekend.

Snowpack Summary

~20cm of recent storm snow combined with moderate to strong Southwest wind has created wind slabs.

A persistent weak layer remains down 50-70cmcm. This interface consists of surface hoar in sheltered locations, a sun crust on solar aspects, and continues to produce moderate-hard sudden results in test profiles.

The base of the snowpack is comprised of several dense, melt-freeze rain crusts formed in October/early November.

Weather Summary

A strong frontal system arrives Tues evening bringing heavy snow and strong wind.

Tonight Trace snow. Light wind

Tues Flurries. Accumulation 7 cm. Alpine high -6 °C. Ridge S 15 km/h. Freezing level (FZL) 1100m.

Wed Snow, heavy at times. 25-30 cm. Alpine high -3. Ridge wind SW25 gusting 70. FZL 1500m.

Thurs Cloudy with sunny periods & isolated flurries. Trace precipitation. Ridge wind SW 15 gusting 40. FZL1100m

Terrain and Travel Advice

  • Look for signs of instability: whumphing, hollow sounds, shooting cracks, and recent avalanches.
  • 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.