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Avalanche Forecast

Archived

Dec 9th, 2020–Dec 10th, 2020

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

Regions

Kootenay Boundary.

A localized pulse dropped moist snow with moderate winds. Investigate the bond of new snow and older surfaces - in some areas it sits on a crust, and other areas possibly surface hoar.

Confidence

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

Weather Forecast

WEDNESDAY NIGHT: Cloudy with isolated flurries, trace to 5 cm / Light variable ridgetop wind / alpine high temperature -4 / Freezing level falling to valley bottom

THURSDAY: Partly cloudy / Light southeast 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

SATURDAY: Sunny breaks / Light southwest 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 deposited up to 20 cm above 1800 m and may overlie a thin crust which developed in areas that received rain or heavy mist before falling temperatures and snowy precipitation.

Warm temperatures moistened the snowpack above 2000 m. At upper (drier) elevations, new snow covers old surfaces of crusts on most slopes, wind-polished and dry, faceted snow on northerly aspects, and a possible layer surface hoar. Early in the week surface hoar developed around the region, and may be especially large in sheltered treeline areas, however in areas where a thin rain crust formed, its likely the wet precipitation crushed the 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.
  • Closely monitor how the new snow is bonding to the old surface.
  • Investigate the bond of the recent snow before committing to your line.

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.