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Avalanche Forecast

Archived

Mar 15th, 2023–Mar 16th, 2023

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

Regions

Yukon, Tutshi, Wheaton, White Pass East, White Pass West.

An intense storm could trigger a natural avalanche cycle. Travel in avalanche terrain is not recommended.

Confidence

Moderate

Avalanche Summary

We haven't received reports of recent avalanche activity. Going forward, we anticipate a natural avalanche cycle over the day on Thursday as snow rapidly accumulates. Avoidance of avalanche terrain is recommended until the storm calms down and the snowpack has time to adjust.

Snowpack Summary

A substantial storm is forecast for Thursday, with forecast snow amounts of 30 to 50 cm by the end of the day. The snow will fall with strong southerly wind, which will make the deepest deposits in lee terrain features near ridges. This snow will fall on previously wind affected snow (sastrugi) in wind affected areas and faceted snow in sheltered features. The new snow may not bond well to these previous surfaces.

The storm will load a buried weak layer of surface hoar about 60 cm deep in Powder Valley, Tutshi, and Paddy Peak areas and up to 140 cm around White Pass. This layer is most prominent on northerly slopes sheltered from the wind. On other aspects, this layer is a hard melt-freeze crust with weak facets around it. To date this layer is has been most problematic in alpine terrain.

The middle of the snowpack is consolidated and strong. Weak faceted grains are found near the base of the snowpack, particularly in thin snowpack areas.

Weather Summary

Wednesday Night

Cloudy with snowfall, accumulation 5 to 10 cm, 20 to 40 km/h south wind, treeline temperature -12 °C.

Thursday

Cloudy with snowfall, accumulation 20 to 40 cm, 60 km/h south wind, treeline temperature -6 °C.

Friday

Cloudy with snowfall then clearing, accumulation 10 to 20 cm, 40 km/h south wind, treeline temperature -5 °C.

Saturday

Early morning snowfall then a mix of sun and cloud, accumulation 2 to 5 cm, 20 to 40 km/h east wind, treeline temperature -5 °C.

More details can be found in the Mountain Weather Forecast.

Terrain and Travel Advice

  • Travel in alpine terrain is not recommended.
  • Watch for fresh storm slabs building throughout the day.
  • Storm slabs in motion may step down to deeper layers resulting in large avalanches.
  • Be aware of the potential for large, deep avalanches to run full path or even longer.

Problems

Storm Slabs

Storm Slab avalanches are the release of a cohesive layer (a slab) of new snow that breaks within new snow or on the old snow surface. Storm-slabs typically last between a few hours and few days (following snowfall). Storm-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.