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Avalanche Forecast

Archived

Feb 17th, 2023–Feb 18th, 2023

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

Regions

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

Carefully assess the wind effect as well as new snow amounts as you move through terrain. Ongoing snowfall and southerly winds are adding to the wind slab problem.

Confidence

Moderate

Avalanche Summary

No significant avalanches were reported in the last couple days. On Thursday our field team observed debris from a previous large persistent slab avalanche. At least once a week evidence of large persistent slab avalanches is reported. Keep this in mind when traveling in the backcountry.

Snowpack Summary

Southerly winds and ongoing snowfall continues to maintain the wind slab problem. Southerly slopes are generally scoured or wind pressed. In sheltered areas the above mentioned snow is still soft and likely makes for decent riding.

A hard melt-freeze crust that extends up to about 1700 m is now on the snow surface in wind-exposed terrain and otherwise buried about 50 to 80 cm in wind-loaded terrain. The crust appears to be bonding to the snowpack.

A weak layer of surface hoar and facets may be buried about 80 to 120 cm deep on north to east aspects in alpine and upper treeline elevations. The layer may rest on a harder melt-freeze crust. Where preserved, this layer has shown to have very high propagation potential and capable of producing large avalanches hundreds of metres wide.

Weather Summary

Friday Night

Cloudy with a few centimeters of new snow expected. Light southwest winds and a Low of -9 at 1500m.

Saturday

Cloudy with up to 10cm of new snow. Moderate to strong southwest winds and a high of -5 at 1500m.

Sunday

A few clouds and the possibility of light flurries bringing a few centimeters of new snow. Light to moderate southwest winds and a high of -6 at 1500m.

Monday

Cloudy with 5 to 10cm of new snow expected. Light northerly winds and a high of -14 at 1500m.

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.
  • Watch for areas of hard wind slab on alpine features.
  • Watch for signs of instability like whumpfing, hollow sounds, shooting cracks or recent avalanches.
  • The best and safest riding will be on slopes that have soft snow without any slab properties.
  • Remote triggering is a big concern, be aware of the potential for wide propagations and large, destructive avalanches at all elevations.

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.