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Avalanche Forecast

Archived

Feb 19th, 2015–Feb 20th, 2015

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

Regions

Glacier.

Weather Forecast

A brief and weak weather system will bring a bit of snow, but the ridge will rebuild on Friday. Today expect clouds and flurries, with gusty west winds at ridgetop. We may receive up to 4cm by Friday morning. Friday will be similar; cloudy with flurries. On Sat the ridge will bring a mix of sun and cloud and cooler temps.

Snowpack Summary

Very challenging travel and ski conditions exist below 1900m. Above 1700m 5-15cm of snow sits on the Feb 14 crust, which exists to ~2200m. Steep solar aspects have a sun crust. Persistent weak layers between 1m to 1.5m are stubborn to trigger but give sudden test results in isolated areas. The mid and lower snowpack is well settled.

Avalanche Summary

No new avalanches were observed yesterday. Recent avalanches were solar triggered. On the weekend, impressive deep slab avalanches occurred. A size 3.5 from the col between Clarke Peak and Mt Swanzy was likely triggered by cornice fall and ran on glacier ice. In the Asulkan Valley, a size 3.0 from Mt Pollux ran on the Nov 9 crust/to ground.

Confidence

Problems

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.

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.