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Avalanche Forecast

Archived

Apr 27th, 2023–Apr 28th, 2023

Alpine
Natural and human triggered avalanches likely.
Treeline
Natural and human triggered avalanches likely.
Below Treeline
Natural and human triggered avalanches likely.
Alpine
Natural and human triggered avalanches likely.
Treeline
Natural and human triggered avalanches likely.
Below Treeline
Natural and human triggered avalanches likely.
Alpine
Natural and human triggered avalanches likely.
Treeline
Natural and human triggered avalanches likely.
Below Treeline
Natural and human triggered avalanches likely.

Regions

Glacier.

Warm temperatures are expected to produce large avalanches, avoid avalanche terrain.

Confidence

High

Avalanche Summary

Numerous moist/wet, loose surface avalanches have been observed throughout the week from steep terrain on all aspects at and below treeline. These point releases gather substantial mass as they move downslope into warmer snow.

Temps and FZLs will continue to climb weakening the snowpack on all aspects and elevations. Expect loose avalanches to increase in size and may step down to deep layers, possibly even the Nov 17 facets.

Snowpack Summary

Warm temperatures and very little overnight refreeze have produced a weak, moist upper snowpack at all elevations. Several crusts are buried 30-50cm but are breaking down as the snow warms up.

Below treeline the snowpack is wet and weak, 20-40cm above the ground the Nov 17 basal weakness can still be found in many areas.

Weather Summary

Warm and sunny weather will continue right through the weekend with above seasonal temperatures and high freezing levels (FZL).

Fri: sunny skies, Alp high 9°C, light winds, FZL 3500m

Sat: sunny skies, Alp high 12°C, light southwest winds, FZL 3600m

Sun: mix of sun and cloud w/ isolated rain showers, Alp high 14°C, light south winds, FZL 3500m.

Terrain and Travel Advice

  • As surface loses cohesion due to melting, loose wet avalanches become common in steeper terrain.
  • If triggered loose wet avalanches may step down to deeper layers resulting in larger avalanches.
  • The more the snowpack warms-up and weakens, the more conservative you`ll want to be with your terrain selection.

Problems

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.

Wet Slabs

Wet Slab avalanches are the release of a cohesive layer of snow (a slab) that is generally moist or wet when the flow of liquid water weakens the bond between the slab and the surface below (snow or ground). They often occur during prolonged warming events and/or rain-on-snow events. Wet Slabs can be very unpredictable and destructive.

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.

Deep Persistent Slabs

Deep Persistent Slab avalanches are the release of a thick cohesive layer of hard snow (a slab), when the bond breaks between the slab and an underlying persistent weak layer deep in the snowpack. The most common persistent weak layers involved in deep, persistent slabs are depth hoar or facets surrounding a deeply buried crust. Deep Persistent Slabs are typically hard to trigger, are very destructive and dangerous due to the large mass of snow involved, and can persist for months once developed. They are often triggered from areas where the snow is shallow and weak, and are particularly difficult to forecast for and manage.