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Avalanche Forecast

Archived

Dec 10th, 2015–Dec 11th, 2015

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

Regions

Glacier.

Don't be surprised by a touchy surface hoar layer that becomes more reactive at lower elevations. While natural avalanches are becoming less likely, storm slabs will still be easily triggered by riders in the right (or wrong) spot.

Weather Forecast

Today expect flurries and temps ranging from -3 to -10. Moderate S'ly winds will continue to load lee slopes. Flurries will taper off on Friday, with the possibility of some sun, which may destabilize the new snow. Late Saturday the next storm will arrive bringing more snow, with freezing levels at valley bottom.

Snowpack Summary

At treeline, 1m of new snow over the past week is settling and overlies a variety of surfaces. At treeline and below it sits on a surface hoar layer. The surface hoar layer is biggest and very reactive below ~1600m. On solar aspects it sits on a sun crust and may bond poorly. Surface hoar layers down ~1.5m are still reactive but harder to trigger.

Avalanche Summary

Yesterday there were reports of the Dec 2 surface hoar being remotely and skier triggered producing up to size 2 avalanches at ~1500m. At treeline and above, pockets of soft windslab have been easily triggered with propagations up to 80m wide. On Tuesday avalanches to size 3.5 were triggered naturally and by avalanche control.

Confidence

Timing of incoming weather systems is uncertain

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.

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.

Loose Dry

Loose Dry avalanches are the release of dry unconsolidated snow and typically occur within layers of soft snow near the surface of the snowpack. These avalanches start at a point and entrain snow as they move downhill, forming a fan-shaped avalanche. Other names for loose-dry avalanches include point-release avalanches or sluffs.