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Avalanche Forecast

Archived

Dec 6th, 2020–Dec 7th, 2020

Alpine
Natural avalanches unlikely.
Treeline
Natural avalanches unlikely.
Below Treeline
Natural avalanches unlikely.
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

South Columbia.

The next storm will start to trickle into the north of the region over the day. If more than 10 cm of new snow falls, avalanche danger will rise to MODERATE in the alpine and wind exposed treeline areas.

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 and over the day Tuesday. Highest snowfall amounts will be in the north of the region.

Sunday night: Increasing cloud with flurries starting in the early morning, moderate southwest wind, freezing level valley bottom to 700 m.

Monday: Up to 10 cm new snow, moderate southwest wind, freezing level 800-1200 m.

Tuesday: 15-30 cm new snow, moderate southwest wind, freezing level 1100 m.

Wednesday: 5-15 cm new snow, light northwest wind, freezing level 1000 m.

Avalanche Summary

Small loose dry sluffing may be observed in the new snow Monday. If more than 10 cm of new snow falls, small storm slabs may be triggerable in wind loaded lee features at upper elevations.

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

Around 5 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 does not appear to be a concern at this time.

Terrain and Travel

  • Be aware of the potential for loose avalanches in steep terrain where snow hasn't formed a slab.
  • Expect slab conditions to change drastically as you move into wind exposed terrain.

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.