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Avalanche Forecast

Archived

Dec 11th, 2020–Dec 12th, 2020

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

Regions

Yukon.

With cold outflow conditions over the weekend the main concern is the formation of new wind slabs. 

Confidence

Moderate - Uncertainty is due to the speed, direction, or duration of the wind and its effect on the snowpack.

Weather Forecast

An arctic front will create outflow conditions over the weekend until the next Pacific frontal system arrives on Monday.

FRIDAY NIGHT: Cloudy, moderate northeast wind, temperatures drop to -15 C.

SATURDAY: Mix of sun and cloud, moderate to strong northeast wind, high temperatures around -10 C.

SUNDAY: Mix of sun and cloud, moderate to strong northeast wind, high temperatures around -10 C.

MONDAY: Frontal system arrives with 5-10 cm of snow, strong southwest wind, high temperatures around -8 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. 

You may also still find evidence of large avalanches that occurred during the big storm at the beginning of December, but these old storm slabs are no longer a problem.

Snowpack Summary

15-30 cm of low density snow has been blowing around over the past few days, and will likely get redistributed with outflow winds over the weekend. Sparse reports suggest this snow is bonding well to old interfaces including a widespread crust. This crust has been reported up to 1400 m in the Wheaton Valley, up to 1800 m near the AK border, but was not evident between 1400-1700 m in the Tutshi area. The main concern over the weekend is fresh wind slabs forming above these crusts.

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 wind-loaded pockets especially around ridgecrest and in extreme terrain.
  • Be aware of highly variable recent wind loading patterns.
  • 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.