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Avalanche Forecast

Archived

Dec 29th, 2021–Dec 30th, 2021

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 possible, human triggered probable.
Below Treeline
Below Threshold.

Regions

Yukon.

Assess snow surface as you venture out. If you see any signs of instability, choose a low angle slope and pick a line where the snow is deepest. 

Confidence

Moderate - Uncertainty is due to the extreme variability of wind effect on the snowpack.

Weather Forecast

A system, approaching from the north, is passing throughout Yukon Wednesday, with light amounts of snow but strong northerly winds. On Thursday, an arctic ridge of high pressure will re-establish itself, leading to another clear and cold day heading into Friday. The next round of snow is expected Saturday.

WEDNESDAY NIGHT: Lingering flurries / Moderate to strong north winds in the alpine / Low of -20

THURSDAY: Clear / Moderate northwest winds in the alpine / High of -18

FRIDAY: Flurries all day / Strong southwest winds in the alpine / High of -14

SATURDAY: Snow 10 cm / Strong southwest winds in the alpine / High of -12

Avalanche Summary

On Wednesday, the poor visibility restricted observations in the alpine.

No new avalanches have been reported in the last few days. 

If you are out in the mountains, please consider filling out a Mountain Information Network repport.

Snowpack Summary

On Wednesday, the region received about 5 cm of new snow along with southwest winds. This new snow has covered hard surfaces such as sastrugi, old wind slabs or recently scoured slopes in the alpine. 

At treeline, the wind also affected the surface, but pockets of powder can be found. All this snow will get redistributed with the incoming northerly winds, creating cross-loading. 

The lower snowpack is made up of weak sugary snow. An avalanche at this interface is most likely to be triggered in shallow areas or with a large impact like a cornice fall or surface avalanche.

Terrain and Travel

  • Keep your guard up at lower elevations. Wind slab formation has been extensive.
  • Watch for newly formed and reactive wind slabs as you transition into wind affected terrain.
  • Back off if you encounter whumpfing, hollow sounds, or shooting cracks.
  • 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.

Deep Persistent Slabs

Deep Persistent Slab avalanches are the release of a thick cohesive layer of hard snow (a slab), when the bond breaks between the slab and an underlying persistent weak layer deep in the snowpack. The most common persistent weak layers involved in deep, persistent slabs are depth hoar or facets surrounding a deeply buried crust. Deep Persistent Slabs are typically hard to trigger, are very destructive and dangerous due to the large mass of snow involved, and can persist for months once developed. They are often triggered from areas where the snow is shallow and weak, and are particularly difficult to forecast for and manage.