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Avalanche Forecast

Archived

Apr 12th, 2021–Apr 14th, 2021

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

Regions

Yukon.

Strong wind and new snow are likely keeping wind slabs reactive. Seek sheltered terrain for the best riding conditions.

Confidence

Moderate - Uncertainty is due to the limited number of field observations. Uncertainty is due to how quickly the snowpack will recover and gain strength.

Weather Forecast

MONDAY NIGHT: Cloudy with snowfall, accumulation 2 to 5 cm, 50 km/h southwest wind, alpine temperature -5 C.

TUESDAY: Cloudy with snowfall, accumulation 2 to 5 cm, 50 km/h southwest wind, alpine temperature -4 C, freezing level rising to 1000 m.

WEDNESDAY: Cloudy with snowfall, accumulation 5 to 10 cm, 60 km/h south wind, alpine temperature -2 C, freezing level 1200 m.

THURSDAY: Partly cloudy, 20 km/h southeast wind, alpine temperature 0 C, freezing level 1500 m.

Avalanche Summary

On Friday, the field team observed natural wind slabs from a steep, alpine south facing gulley features around White Pass. They were also able to remotely triggered multiple size 1 to 2 wind slabs, with the furthest avalanche releasing 350m away! The reactive wind slabs ran on a 2 cm thick melt-freeze crust down 30 to 70 cm. On Saturday, the field team continued to investigate these slabs, found them to be reactive (see here), and suspected they would be so for a few more days.

Snowpack Summary

Around 15 cm of snow from Friday was redistributed by strong northeast wind in exposed terrain, forming touchy wind slabs everywhere except in sheltered terrain. The wind effect is particularly widespread along the highway corridor at White Pass but may be less so as you push into the side valleys from the highway. The slabs overly a hard melt-freeze crust on sun-exposed slopes up to 1300 m. New snow on Monday through Wednesday will be accompanied by strong southwest wind, likely keeping wind slabs reactive above the rain-snow line.

The White Pass area has a deep snowpack without any deeper layers of concern. The Tutshi Lake / Paddy Peak area should be assessed on a slope by slope basis, as some lingering snowpack weaknesses may still exist on isolated slopes. The Wheaton's shallower snowpack is dominated by hard wind slabs overlying sugary facets and depth hoar. It's an untrustworthy snowpack structure that requires conservative terrain selection and diligent travel habits. 

Terrain and Travel

  • Watch for newly formed and reactive wind slabs as you transition into wind affected terrain.
  • Recent wind has varied in direction so watch for wind slabs on all aspects.
  • Seek out sheltered terrain where new snow hasn't been wind-affected.
  • Pay attention to cornices and give them a wide berth when traveling on or below ridges.

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.