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Avalanche Forecast

Archived

Dec 12th, 2020–Dec 14th, 2020

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

Regions

Yukon.

The main thing to look out for is newly-formed wind slabs from increasing and variable wind along with some new snow on Monday.

Confidence

Moderate - Uncertainty is due to the limited number of field observations.

Weather Forecast

SATURDAY NIGHT: Mostly cloudy, 20 km/h south wind, alpine temperature -10 C.

SUNDAY: Mostly cloudy, 20 to 40 km/h south wind, alpine temperature -10 C.

MONDAY: Cloudy with snowfall, accumulation 5 to 10 cm, 40 to 60 km/h southwest wind, alpine temperature -10 C.

TUESDAY: Cloudy with light snowfall, accumulation 5 cm, 20 km/h southeast wind, alpine temperature -11 C.

Avalanche Summary

A MIN report from Wednesday shows some small wind slab avalanches on northeast slopes in the Tutshi area. This activity is indicative of the type of avalanches that are possible this weekend, although with shifting winds they are now possible on all aspects.

Snowpack Summary

Soft snow can be found in sheltered terrain whereas hardened wind slabs are likely found in the alpine and exposed treeline. An increasing wind speed trend on Sunday into Monday may allow for further formation of wind slabs, particularly with some new snowfall on Monday. Below this surface snow lies a widespread melt-freeze crust. The crust has been reported up to 1400 m in the Wheaton Valley, up to 1800 m near the Alaska border, but was not evident between 1400-1700 m in the Tutshi area. The main concern is newly-formed wind slabs sitting on this crust.

The lower snowpack is generally settled and strong after a massive storm at the beginning of December. However, there is potential for weak snow at the bottom of the snowpack in colder drier areas such as the Wheaton Valley. We have minimal data from these areas, but recommend extra caution around shallow rocky slopes in thinner snowpack areas.

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.
  • Avoid shallow, rocky areas where the snowpack transitions from thick to thin.

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.