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Avalanche Forecast

Archived

Mar 17th, 2024–Mar 18th, 2024

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

Regions

Glacier.

Avoid avalanche terrain!

Strong sunshine and above freezing alpine temperatures are causing a widespread natural avalanche cycle

Widespread large natural avalanches are expected

Confidence

High

Avalanche Summary

Since the warm up began on Friday we have seen numerous loose and wet slab avalanches from solar aspects, some very large and failing on the Feb 3rd layer. Notably a size 4 from the west face of Cheops and size 3 beside the Grizzly couloir

Expect natural avalanches to increase in size and frequency with continued warming.

Natural avalanches on the persistent weak layer (over 1m deep) are expected to become widespread as the warmth penetrates deeper into the snowpack.

Snowpack Summary

Expect a very thin crust to form overnight that will break down quickly by mid morning from above zero temps and intense sun. When that happens the upper snowpack will turn to mush.

A previous suncrust, down 20-40cm, may make a sliding layer for wet slabs.

80-140cm of settled snow sits above a sugary facet layer. These facets are poorly bonded to the widespread, firm crust from Feb 3rd. This is a significant persistent weak layer and will be a concern for the foreseeable future.

Weather Summary

The warm weather will continue for two more days keeping the avalanche danger high. By mid week the freezing level (FZL) will begin to lower and temps return to more seasonal values and snow on Wednesday.

Tonight: Alpine low 2°C, light W winds, FZL 1100m with a temperature inversion.

Mon: Warm and sunny, low 1°C, high 3°, FZL 2700m, light W winds.

Tues: Mix of sun and cloud, low 1°C, high 4°C, FZL 2100m, light W winds.

Terrain and Travel Advice

  • Avoid exposure to overhead avalanche terrain as temperatures increase.
  • If triggered loose wet avalanches may step down to deeper layers resulting in larger avalanches.
  • Avoid exposure to slopes that have cornices overhead.
  • Avoid traveling in runout zones. Avalanches have the potential to run to the valley floor.

Problems

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.

Loose Wet

Loose Wet avalanches are the release of wet unconsolidated snow or slush. These avalanches typically occur within layers of wet snow near the surface of the snowpack, but they may quickly gouge into lower snowpack layers. Like Loose Dry Avalanches, they start at a point and entrain snow as they move downhill, forming a fan-shaped avalanche. Other names for loose-wet avalanches include point-release avalanches or sluffs. Loose Wet avalanches can trigger slab avalanches that break into deeper snow layers.

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.