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Avalanche Forecast

Archived

Dec 4th, 2014–Dec 5th, 2014

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

Regions

South Rockies.

Forecast confidence is very poor, we desperately need your observations right now. Please email them to [email protected]

Confidence

Poor - Due to the number of field observations

Weather Forecast

Synopsis: A pattern shift is underway as dry and cold northwest flow gives way to rather mild southwest flow. Storm totals through the weekend look pretty bleak for the Rockies, but the door appears to be open to a succession of storms through the middle of next week.Friday: Freezing Level: Valley Bottom; Precipitation: Nil Trace; Wind: Treeline: Moderate, SW | Ridgetop: Strong, SWSaturday: Freezing Level: 500m with potential for above freezing temps between 1000m and 2000m; Precipitation: 0-1mm | trace; Wind: Treeline: Strong, SW | Ridgetop: Extreme, SW Sunday: Freezing Level: 1500m; Precipitation: 0-2mm | trace-2cm; Wind: Treeline: Moderate, SW | Ridgetop: Moderate, W/SW

Avalanche Summary

The last activity I heard tell of was an explosive trigged size 2 storm slab on a high elevation N-NE aspect. (read: old news) Seen anything more recent?

Snowpack Summary

As we begin our forecasting season, we are working with almost no field data. If you have been out in the mountains, we'd love to hear from you. There is at least one, maybe more, problematic layers in the South Rockies snowpack. Last weekends 30 - 60cm of storm snow buried a weak layer of facets over a crust which formed during November's dry spell. That interface is probably around a meter down now. Not much us known about the reactivity of this layer, nor the slab above it. But, it doesn't take much of a leap of faith to understand that a meter deep slab sitting on a persistent weak layer is a potentially bad thing.This forecast isn't going to get much better until we get some field observations. If you've got some, please send them in. Eventually you'll be able to use the Mountain Information Network, but for now please email your obs to: [email protected] THANKS!

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.