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Avalanche Forecast

Archived

Nov 26th, 2014–Nov 27th, 2014

Alpine
Natural and human triggered avalanches likely.
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.

High avalanche danger. Deep storm slabs have developed quickly at higher elevations. Weak layers of sugary facets below the storm slabs has resulted in easy triggering of potentially large avalanches.

Confidence

Poor - Timing, track, or intensity of incoming weather system is uncertain

Weather Forecast

A series of storms is expected to continue to move across the interior mountain ranges from the coast. There should be periods of moderate snowfall during the day on Thursday as the next big pulse of moisture and strong Southwest winds pushes East of the continental divide. Eastern parts of the region may dry out and cool down quickly as arctic air descends from the North. If your area gets heavy snowfall on Thursday you should consider it to be more like the Lizard and Flathead region. By Saturday it should be mostly cold with some lingering cloud and light snow.

Avalanche Summary

No avalanche activity has been reported. This may speak more to a lack of observations rather than actual conditions. In the neighboring Lizard/Flathead region, natural and human-triggered avalanches to size 2 have failed on basal facets. I suspect a similar pattern of avalanche activity may be developing in some of the deeper snowpack areas within this region. With forecast weather, I expect continued storm slab activity with the potential to trigger deeper, more destructive weaknesses at the base of the snowpack.

Snowpack Summary

As we begin our forecasting season we are working with very limited field data. If you have been out in the mountains, please send us a note with your observations to [email protected] limited field data that we have received suggests that there is not enough snow below treeline for avalanche activity. At higher elevations, the developing storm slab may be sitting on a weak layer of facetted snow, surface hoar, and/or a wind or sun crust that developed earlier in the month. This storm slab has been touchy to human triggers and has been reactive on basal facets in the Lizard/Flathead Region. I would expect similar conditions in some of the deeper snowpack areas within the South Rockies region.I expect avalanche activity to increase in size and frequency with forecast wind, snow and warming.

Problems

Storm Slabs

Storm Slab avalanches are the release of a cohesive layer (a slab) of new snow that breaks within new snow or on the old snow surface. Storm-slabs typically last between a few hours and few days (following snowfall). Storm-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.