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Avalanche Forecast

Archived

Feb 19th, 2023–Feb 20th, 2023

Alpine
Natural and human triggered avalanches likely.
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 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.

Numerous human-triggered and natural storm slabs occurred on Sunday. This problem will remain reactive for a few days with continuing inputs of snow and wind.

Limit your exposure to overhead hazards like cornices, large slopes, or other groups in the area.

Confidence

Moderate

Avalanche Summary

On Sunday the field team remotely triggered (from the ridge) several storm slabs in steep gully features on Mt. Fidelity, sz 2-2.5, with crown depths of 30-40cm.

Explosive hand charge testing also produced results up to size 2, with crown depths of 30-50cm.

Planned avalanche control on Sunday night will likely produce many size 2-3.5 storm slab avalanches.

Snowpack Summary

15-20cm of new snow has fallen, bringing the storm snow total to ~60cm. Moderate-strong Westerly winds have formed fresh slabs in the alpine and at tree line. Low-density, deep snow is found in sheltered areas.

Several thin crusts are buried on steep solar aspects.

The deep persistent weakness at the base of the snowpack (rounding facets and a crust in some locations), has been showing signs of strengthening recently.

Weather Summary

Another 20cm of snow starting Monday midday and continues into Tuesday morning. Winds will start from the Southwest at 30-70km/hr, then switch over to the East at 20-30km/hr as the storm tapers off.

Cold temps arrive Tuesday and will persist until the end of the week.

Terrain and Travel Advice

  • Storm slabs in motion may step down to deeper layers resulting in large avalanches.
  • Loose avalanches may start small but they can grow and push you into dangerous terrain.
  • Avoid exposure to slopes that have cornices overhead.

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.

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.

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.