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Avalanche Forecast

Archived

Dec 5th, 2013–Dec 6th, 2013

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

Regions

South Rockies.

Observations are limited right now. If you've been out, please tell us what you see by dropping us an email at [email protected]

Confidence

Poor - Due to the number of field observations

Weather Forecast

Extremely cold, dry weather will persist through the weekend, with lows down to -35C. Some cloud on Friday and Sunday; Saturday currently looks clear. Winds initially light but picking up on Saturday afternoon to become strong NW at ridgetop on Sunday.

Avalanche Summary

No reports of avalanche activity.

Snowpack Summary

The limited information we have from this regions suggests treeline snowpack depths vary from around 60 cm to 120 cm depending on location. Anywhere from 40 to 70 cm new snow fell with the most recent storm. Initially temperatures were relatively warm, then they cooled dramatically. As a result, the new storm snow is generally "right-side-up", meaning lower density snow sits above denser snow below. Strong northerly winds following the storm created wind slabs on exposed southern slopes. One recent reports has suggested it is becoming more difficult to trigger these wind slabs. While this is consistent with what we commonly see when the wind subsides and temperatures dive into the -20's, the lack of observations would make me approach steep, wind loaded terrain with a lot of caution right now. At or near the base of the snowpack, I suspect you will find sugary facets. The chance of triggering this layer is quite small under the current conditions, but if it was to happen, it would most likely be on a steep, convex slope with a thin snowpack.

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.