Avalanche Forecast

Archived

Mar 6th, 2013–Mar 7th, 2013

Alpine

Natural avalanches possible, human triggered probable.

Treeline

Natural avalanches possible, human triggered probable.

Below Treeline

Natural avalanches unlikely, human triggered possible.

Alpine

Natural avalanches possible, human triggered probable.

Treeline

Natural avalanches possible, human triggered probable.

Below Treeline

Natural avalanches unlikely, human triggered possible.

Alpine

Natural avalanches possible, human triggered probable.

Treeline

Natural avalanches possible, human triggered probable.

Below Treeline

Natural avalanches unlikely, human triggered possible.

Regions

Glacier.

Large skier triggered avalanches are still possible! Be aware of the terrain you are in, look for overhead hazards. Be aware of the effects of solar radiation today.

Weather Forecast

A weak upper ridge will linger over the area today, bringing mostly sunny skies. A weak low will move through late this afternoon or evening, bringing cloud and a chance of flurries. Clearing skies are again expected for Thursday. Watch for locally strong solar radiation on solar aspects.

Snowpack Summary

Last weeks' storm snow has settled out rapidly over the past two days. Below treeline, a rain crust and substantial tree bombs have created treacherous travel in some places. In the alpine, soft slabs overly the Feb. 12 PWL, now down over a meter and continues to be a concern, especially on solar aspects. Wide propagations are still possible.

Avalanche Summary

Natural avalanche activity has decreased however large avalanches are still possible. We are entering a period of "low probability, high consequence" avalanche behavior, in which the likelihood of triggering is less than it was during the storm, but the chance that a skier can trigger a very large avalanche is still very possible. See photo:

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.