Dashboard Regions Weather Stations Radar Alerts Glossary
Contact About
Log In

Register for an account and never miss a forecast again!

Register

Avalanche Forecast

Archived

Dec 11th, 2021–Dec 12th, 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 unlikely, human triggered possible.
Treeline
Natural avalanches unlikely, human triggered possible.
Below Treeline
Below Threshold.

Regions

Yukon.

Even though danger ratings are moderate there's still potential problems. Avoid windloaded terrain and stay away from areas with a shallow or variable depth snowpack. Please post to the Mountain Information Network if you are in the mountains. 

Confidence

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

Weather Forecast

Dig out your cold weather clothes--looks like an arctic deep freeze is on its way.

Saturday night: Cloudy with flurries, temperature dropping to -22 overnight. Wind Northeast 30kph 

Sunday: Cloudy with flurries, -25, wind northeast 15-30kph 

Sunday night: Cloudy with a few flurries, -31, wind NE 30-50

Monday: Arctic ridge building. Probably some lingering cloud, temperature -25 to -30, northeast outflow winds expected to continue. 

Avalanche Summary

Explosive control earlier in the month produced many large avalanches that failed on the weak sugary crystals at the bottom of the snowpack. These avalanches ran full path.

On December 1, a size 2.5 avalanche was remotely triggered by a recreational group on Log Cabin. This avalanche likely failed on the weak, sugary snow at the bottom of the snowpack. 

Natural avalanche activity and human triggered avalanches will be most likely in wind-loaded features anywhere recent winds have redistributed the snow. Triggering the deep layer (see the December 1 avalanche described above) is most likely to occur in shallow areas or where the snowpack variable in depth with a mix of shallow and deep zones. 

Snowpack Summary

Low density snow from the last storm is being redistributed by winds that were at first southerly then switched to north and northeasterly. Old windslabs on northerly aspects are likely becoming somewhat less sensitive but expect new, potentially somewhat more sensitive windslabs on south and southwest aspects. Snow quality will be best in sheltered areas, which is also where you are least likely to find windslab problems. 

The middle snowpack is supportive to travel but snow depth still varies greatly with aspect and elevation. 

A layer of weak, sugary snow at the base of the snowpack has been observed in most areas. This layer was reactive earlier in December and it might still be possible to trigger this deeply buried layer in shallow snowpack areas or if a cornice fall or surface avalanche impacts a slope. If triggered, this basal layer could produce large avalanches. This sugary layer will likely become weaker in the coming days with increasingly cold temperatures potentially making it increasingly sensitive to triggering.

Terrain and Travel

  • Watch for newly formed and reactive wind slabs as you transition into wind affected terrain.
  • Be alert to conditions that change with elevation and wind exposure.
  • Approach lee and cross-loaded slopes with caution.
  • Back off if you encounter whumpfing, hollow sounds, or shooting cracks.
  • Be aware of the potential for large avalanches due to the presence of a deep persistent slab.

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.