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Avalanche Forecast

Archived

Apr 5th, 2023–Apr 6th, 2023

Alpine
Natural avalanches unlikely, human triggered possible.
Treeline
Natural avalanches unlikely.
Below Treeline
Below Threshold.
Alpine
Natural avalanches unlikely.
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, Tutshi, Wheaton, White Pass East, White Pass West.

Wind slabs remain the primary concern as light snowfall and strong wind continues. Watch for wind slabs around ridgelines and in mid slope terrain features in areas that see stronger winds.

Confidence

Moderate

Avalanche Summary

Reactive wind slabs were reported on Sunday at alpine elevations in north facing terrain.

On Saturday a rider triggered a cornice fall from a distance, which produced a size 3 persistent slab avalanche on a northeast aspect at 1750 m. The avalanche was 200 cm deep and was suspected to have failed on a layer of facets above a crust buried in January.

Let us know what you are seeing by submitting a report to the Mountain Information Network.

Snowpack Summary

Gradual accumulations of fresh snowfall will be redistributed by southerly winds into wind slabs over previously wind affected snow on north and east facing slopes. South facing terrain will likely be stripped back to a crust by these winds.

A weak layer of surface hoar/crust/facets buried in early January is now over 1 m deep in most areas. This layer has produced recent avalanche activity and remains a concern in terrain where the snowpack is thin.

The lower snowpack consists of basal facets, particularly in shallow areas.

Weather Summary

Wednesday Night

Cloudy with up to 5 cm. Moderate to strong southerly winds. Freezing levels drop to 500 m.

Thursday

Cloudy with up to 5 cm. Moderate to strong southerly winds. Freezing levels around 1200 m.

Friday

Mostly cloudy with trace amounts of snowfall. Moderate southerly winds. Freezing levels remain below 1000 m.

Saturday

Light snowfall returns with strong to extreme southerly winds. Freezing levels around 1000 m.

More details can be found in the Mountain Weather Forecast.

Terrain and Travel Advice

  • Watch for newly formed and reactive wind slabs as you transition into wind affected terrain.
  • Carefully evaluate steep lines for wind slabs.
  • Use caution on large alpine slopes, especially around thin areas that may propagate to deeper instabilities.
  • 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.

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.