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Avalanche Forecast

Archived

Feb 19th, 2023–Feb 20th, 2023

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

Regions

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

Seek out wind-sheltered terrain where you can avoid wind slabs and find great riding.

The lingering potential for large persistent slab avalanches is best managed through low-consequence terrain selection and good travel habits.

Confidence

Moderate

Avalanche Summary

No significant avalanches were reported in the last couple of days but we suspect rider-triggerable wind slabs will be found in exposed terrain.

Last 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 travelling in the backcountry.

Snowpack Summary

Up to 30 cm of recent snowfall remains loose and powdery in sheltered areas. In wind-affected areas, variable winds may have created wind slabs on all aspects. This recent snow sits above a decomposing crust up to 5cm thick that is widespread to 1300 m and can be found up to 1700 m in isolated areas. This crust sits on the surface in wind-exposed terrain and is otherwise buried about 50 to 80 cm in wind-loaded terrain. The crust appears to be bonding to the snowpack.

In alpine and upper treeline elevations, a weak layer of surface hoar and facets may be buried about 80 to 120 cm deep on north-to-east aspects. This layer may rest on a harder melt-freeze crust. Where preserved, this layer is capable of producing large avalanches hundreds of metres wide.

Weather Summary

Sunday night

Cloudy with snowfall, up to 5 cm of accumulation. Ridgetop winds becoming northerly 10-25 km/h by morning. Alpine temperatures drop to -12 ºC.

Monday

Mainly cloudy with isolated flurries.  Ridgetop winds north 20 km/h. Alpine temperatures around -15ºC.

Tuesday

A ridge of high pressure building over the region will bring clear skies and dry conditions. Ridgetop winds north 20 km/h. Alpine temperatures -16ºC rising to -10ºC in the afternoon.

Wednesday

The ridge maintains over the region with clear skies, winds north becoming southwesterly 20 km/h.  Alpine temperature -20ºC increasing to -10ºC in the afternoon.

More details can be found in the Mountain Weather Forecast.

Terrain and Travel Advice

  • Recent wind has varied in direction so watch for wind slabs on all aspects.
  • Watch for signs of instability like whumpfing, hollow sounds, shooting cracks or recent avalanches.
  • Pay attention to cornices and give them a wide berth when traveling on or below ridges.
  • The best and safest riding will be on slopes that have soft snow without any slab properties.

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.