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Avalanche Forecast

Archived

Dec 4th, 2013–Dec 5th, 2013

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

Regions

South Rockies.

Confidence

Fair - Due to the number of field observations

Weather Forecast

Mostly clear and cold for the forecast period. There is a chance of some cloud and very light flurries in the Southeast.

Avalanche Summary

No reports of avalanche activity. We suspect that the storm slab continues to be reactive to human triggers where it is sitting on a weak layer of buried surface hoar, facetted crystals, or crust.

Snowpack Summary

A storm slab has developed above the existing shallow weak snowpack. We don't know how deep the storm slab is due to a lack of observations from the field. I expect that there is 10-40 cm of new snow depending on your location in the region. This variability is due to the convective nature of the recent storm. The new storm slab is not expected to bond well to the old surface weak layers of crusts, wind slabs, and surface hoar.

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.