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Avalanche Forecast

Archived

Dec 8th, 2020–Dec 9th, 2020

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

Regions

Kootenay Boundary.

A band of moisture with push through the region overnight, depositing up to 30 cm with moderate winds. This may be a very localized system - in areas accumulating less than 20 cm avalanche hazard will likely be a step down.

Confidence

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

Weather Forecast

A localized band of moisture with push through the region overnight, with potentially up to 30 cm fresh snow.

TUESDAY NIGHT: Cloudy with flurries, 10-30 cm / Moderate southwest ridgetop wind / alpine low temperature -6 / Freezing level dropping to 1000 m

WEDNESDAY: Cloudy with isolated flurries, trace to 5 cm / Light variable ridgetop wind / alpine high temperature -4 / Freezing level 900 m

THURSDAY: Partly cloudy / Light south ridgetop wind / alpine high temperature -5 / Freezing level valley bottom

FRIDAY: Sun and cloud / Light south ridgetop wind / alpine high temperature -6 / Freezing level valley bottom

Avalanche Summary

There have been no recent avalanche observations.

Other than a few small loose-wet avalanches from steep terrain on the last few sunny days, the last avalanche observations were Wednesday Dec 2 when warming likely triggered numerous wet loose avalanches from NE slopes above 2000 m.

Have you been out and about in the mountains? If so please submit to the Mountain Information Network (MIN). It doesn't have to be technical it can be as simple as a photo. Photos are especially helpful! Sending a big thank you to the already submitted MIN's this season!

Snowpack Summary

A localized band of moisture and wind with pushed through the region overnight, depositing up to 30 cm fresh snow in localized areas. A thin crust may have developed in areas that received rain or heavy mist.

New snow will cover the old surfaces of crusts on most slopes, wind-polished and dry, faceted snow on northerly aspects around treeline and higher, and widespread surface hoar. Over the last few days, surface hoar has been observed developing around the region, and may be especially large in sheltered treeline areas - as new snow and wind develops slabs, it will be most reactive where sits over surface hoar.

Crusts from mid-and early-November are generally found 30 cm below the snow surface and 10 cm up from the ground at all elevations. While they are showing resistant planar results in snowpack tests, a lot of uncertainty still exists with limited observations and while we don't think they're currently a problem, we're not ready to throw them out yet. Snowpack depths vary with elevation, treeline averages between 50-100 cm. 

Terrain and Travel

  • Be careful with wind loaded pockets, especially near ridge crests and roll-overs.
  • Give the new snow time to settle and stabilize before pushing into bigger terrain.
  • Closely monitor how the new snow is bonding to the old surface.

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.