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Avalanche Forecast

Archived

Feb 10th, 2013–Feb 11th, 2013

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

South Rockies.

Confidence

Good

Weather Forecast

Monday: The pattern and flow starts changing today as the ridge move southward and a zonal flow sets up. An embedded cold front will move through the region bringing moderate NW winds and a trace of snow. Treeline temperatures will sit near -5 and freezing levels will be around 1800 m. Tuesday: The fast paced zonal flow will continue with a trough moving in from the West bringing moderate-strong NW winds and light snow accumulations. Treeline temperatures will be near -8 and freezing levels around 1800 m.Wednesday: Another ridge is building bringing dryer conditions, especially for the short term. Ridgetop winds will be light from the West. Treeline temperatures -10 and freezing levels falling to valley bottom. 

Avalanche Summary

No new natural avalanche observations reported. On Saturday, the only notable events occurred in the Lizard Range with a couple skier triggered wind slabs size 1-1.5, the crown depth was 20-30 deep and 15-20 m wide. Slab showed decent propagation. There were also a few size 1 loose snow avalanches were reported running out of steep terrain.

Snowpack Summary

Up to 15 cm of recent snowfall has been redistributed into dense or hard wind slabs at higher elevations from variable winds. A hard sun crust is likely on steep solar aspects. The new storm snow overlies old wind slabs in exposed areas, settled storm snow or spotty surface hoar in more sheltered terrain, and a crust on previously sun-exposed slopes. A variable interface (surface hoar/facets/sun crust) was buried on Jan 23 and is down about 20-40cm. In most locations it now appears to be well bonded. The lower snowpack is generally well-settled.Cornices in the region are reported to be well developed and loom over heavily used slopes.

Problems

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.

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.