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Avalanche Forecast

Archived

Dec 6th, 2020–Dec 7th, 2020

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

Regions

North Columbia.

The new snow is not expected to bond well to old surfaces. Watch for sluffing out of steep terrain, and fresh storm slabs in wind loaded lee features. 

In areas where more than 20 cm falls, avalanche danger will rise to CONSIDERABLE at alpine and treeline elevations.

Confidence

Moderate - Uncertainty is due to the timing, track, & intensity of the incoming weather system.

Weather Forecast

The incoming storm will deliver the bulk of its goods on Monday night. Highest snowfall amounts will be in the north of the region; the Monashees east of Blue River and the Adamants. 

Sunday night: Trace to 5 cm new snow, moderate southwest wind, freezing level 500 m.

Monday: 5-10 cm new snow in most areas with hot sports in the north receiving 15+ cm. Strong southwest wind, freezing level 1000 m.

Tuesday: 20-30 cm new snow, moderate to strong southwest wind, freezing level 1300 m.

Wednesday: Around 5 cm new snow, light northwest wind, freezing level 1000 m.

Avalanche Summary

On Monday, small storm slabs may be triggerable in freshly wind loaded lee features at upper elevations. Loose dry sluffing may be observed out of steep terrain, especially with human traffic.

Our eyes and ears in the mountains are limited this winter due to fewer professional observations. If you go out in the mountains, please share your observations on the Mountain Information Network (MIN). Photos are especially helpful! Thank you so much for all the great MINs submitted so far!

Snowpack Summary

5-15 cm of new snow falls ontop of a melt-freeze crust on south aspects and widespread surface hoar. Generally speaking, new snow does not bond well to these types of surfaces.

The lower snowpack is characterized by a couple of crusts, the most notable of which is sitting near the base of the snowpack, likely surrounded by a weak layer of sugary facets. It is most likely to be reactive to human triggers on south facing slopes and in shallow, rocky areas in the alpine.

Terrain and Travel

  • Storm snow and wind is forming touchy slabs. Use caution in lee areas in the alpine and treeline.
  • Be aware of the potential for loose avalanches in steep terrain where snow hasn't formed a slab.
  • Dial back your terrain choices if you are seeing more than 20 cm of new snow.

Problems

Storm Slabs

Storm Slab avalanches are the release of a cohesive layer (a slab) of new snow that breaks within new snow or on the old snow surface. Storm-slabs typically last between a few hours and few days (following snowfall). Storm-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.