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Avalanche Forecast

Archived

Dec 12th, 2018–Dec 13th, 2018

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

Regions

Kootenay Boundary.

Strong wind, continued snowfall and a rising freezing level are testing our young snowpack. No one knows exactly how this will all play out. Conservative terrain selection is key while the mountains adjust in this time of great change.

Confidence

Low - Timing, track, or intensity of incoming weather system is uncertain on Thursday

Weather Forecast

The next storm will bring snow and wind to the Boundary region late Wednesday into Thursday. Another system is expected Friday night. Each storm will bring a slightly warmer air mass driving the freezing level up the mountainside.WEDNESDAY NIGHT: Freezing level around 500 m, strong southwest wind, 2 to 8 cm of snow.THURSDAY: Overcast, freezing level around 500 m rising to 1000 m, strong southwest wind, 8 to 15 cm of snow.FRIDAY: Broken cloud cover clearing to a few clouds in the evening, freezing level beginning around 1500 m potentially rising has high as 2200 m, strong south wind, trace of precipitation. 5 to 15 cm of snow/rain at lower elevations on Friday night.SATURDAY: Overcast clearing to scattered cloud cover in the evening, freezing level holding around 1500 m, strong southwest wind slowing to light wind near sundown, trace of precipitation.

Avalanche Summary

A natural size 2 storm slab was reported Wednesday morning on a southeast facing slope at 2000 m. Control work Wednesday produced storm slabs to size 2.5 on southeast through southwest facing features near 2000 m.On Tuesday natural and skier triggered avalanches to size 2 were reported from SE facing features around 2000 m, running on the December 10th surface hoar.Big thanks go out to our contributors to the Mountain Information Network. Please continue to post your observations here.

Snowpack Summary

The region picked up 20 to 40 cm of new snow with moderate to strong southwest wind Tuesday into Wednesday. This new snow rests on a variable weak layer of surface hoar, facets and a rain crust which we are calling the December 10th layer. This layer has been observed at all elevations.Below the facets, a stacked pair of persistent weak layers is buried 50 to 90 cm down. The upper layer consists of surface hoar (feathery crystals) in most places, but may present as a sun crust on steep south facing slopes. The deeper layer features surface hoar above a widespread temperature crust. Both layers are thought to be widespread at treeline and may also extend into sheltered alpine terrain. These layers are trending towards dormancy, but may remain problematic on steep solar aspects.

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.