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Avalanche Forecast

Archived

May 3rd, 2021–May 5th, 2021

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

Regions

Yukon.

Avalanche conditions likely vary with elevation. Wind slabs will likely form in the alpine and loose wet activity is possible at lower elevations.

Confidence

Moderate - Uncertainty is due to difficult to forecast freezing levels.

Weather Forecast

MONDAY NIGHT: alpine -2C, wind south 30 km/hr, mostly cloudy, 2cm snow

TUESDAY: alpine low -2C high -2C, wind south 30 km/h, cloudy, 10cm new snow in the alpine, possible rain at highway elevation

WEDNESDAY: alpine low -3C high -1C, wind southeast 20 km/h, partly cloudy, freezing levels 1600m

THURSDAY: alpine low -2C high 2C, wind north 15 km/h, mostly cloudy, light precipitation, 2 to 5 cm accumulation, rain possible at highway elevation later in the day

Avalanche Summary

Small (size 1) skier cut wind slab avalanches were reported on Saturday in the high alpine. A size 1.5 wet slab avalanche was reported on Sunday. This slab released from steep, rocky, south facing terrain and ran into lower angle terrain in the valley.

Snowpack Summary

Above 1600 m, around 20 cm of wind pressed dry snow may be found, which overlies a hard melt-freeze crust or other hard surfaces. Below 1600 m, the upper snowpack is wet from recent rain and warm air. The snowpack is isothermal near highway elevations but has still be supporting travel on sleds and skis.

The lower snowpack in White Pass is deep for this time of year with no layers of concern. Areas further inland, such as the Wheaton Valley, may have a shallower and weaker snowpack.

Cornices are still very large. Recent cold temperatures have kept cornice failures to a minimum but they should always be treated with respect in the spring, especially when the air temperature rises.

Terrain and Travel

  • Watch for wind-loaded pockets especially around ridgecrest and in extreme terrain.
  • Be carefull around freshly wind loaded features.
  • Avoid exposure to slopes that have cornices overhead.
  • Firm cornices can pull back into flat terrain at ridgetop if they fail.
  • Keep in mind that wet avalanches can be destructive due to their high density.

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.

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.