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Avalanche Forecast

Archived

Mar 18th, 2016–Mar 19th, 2016

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, human triggered possible.
Alpine
Natural and human triggered avalanches likely.
Treeline
Natural avalanches possible, human triggered probable.
Below Treeline
Natural avalanches possible, human triggered probable.

Regions

Glacier.

Watch for changes in stability as the spring sun warms the snowpack. Persistent avalanche problems remain touchy on unsupported and exposed features above treeline.

Weather Forecast

An upper ridge of high pressure dominates the weather today bringing the spring sun and freezing levels below 1500m. No precipitation is expected and ridge winds will remain light. Freezing levels begin to rise this weekend as the ridge breaks down and another low pressure system moves in.  Freezing levels peak at 2500m on Sunday with light rain.

Snowpack Summary

Convective flurries over the past week have added to the storm slab, with 30-50cm overlying a crust on solar aspects. Persistent weak layers from February are down 70-120cm and are of most concern on solar aspects. On northerly aspects the snowpack has less layers of concern, although on lee features in the alpine buried wind slabs may exist.

Avalanche Summary

Artillery avalanche control procured several size 1.5 to 2.0 avalanches and one large size 3.0 avalanche.  3 size 2.0 natural avalanches were observed in the highway corridor.

Confidence

Timing or intensity of solar radiation 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.

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.

Cornices

Cornice Fall is the release of an overhanging mass of snow that forms as the wind moves snow over a sharp terrain feature, such as a ridge, and deposits snow on the downwind (leeward) side. Cornices range in size from small wind drifts of soft snow to large overhangs of hard snow that are 30 feet (10 meters) or taller. They can break off the terrain suddenly and pull back onto the ridge top and catch people by surprise even on the flat ground above the slope. Even small cornices can have enough mass to be destructive and deadly. Cornice Fall can entrain loose surface snow or trigger slab avalanches.