Avalanche Forecast

Issued: Dec 12th, 2017 4:32PM

The alpine rating is moderate, the treeline rating is moderate, and the below treeline rating is moderate. Known problems include Loose Wet, Storm Slabs and Deep Persistent Slabs.

Avalanche Canada swerner, Avalanche Canada

High freezing levels continue but precipitation amounts overnight Tuesday vary through the region. If you receive more than 20 mm consider the avalanche danger to be CONSIDERABLE.

Summary

Confidence

Moderate - Forecast snowfall amounts are uncertain

Weather Forecast

Wednesday: Mostly cloudy with sunny breaks. Alpine temperatures near plus 5 degrees and freezing levels up to 3000 m. Ridgetop winds moderate from the south.Thursday: Moderate precipitation amounts. Alpine temperatures high of plus 6 degrees with freezing levels 2500 m. Ridgetop winds strong from the southwest. Friday: Cloudy with some flurries. Alpine temperatures near -3 and freezing levels dropping to 800 m. Ridgetop winds light gusting strong from the southwest.Check out the Mountain Weather Forecast for more detail.

Avalanche Summary

On Monday, numerous natural wet slab avalanches up to size 2.5 were reported from upper elevations. Avalanche activity will likely increase through the forecast period with new rain, snow and wind.I'd also remain suspect of the deep persistent layers on your radar as the region receives this new load. On December 7th and 8th a few deep persistent slabs to size 3 out of steep south facing alpine terrain in the Skeena corridor west of Terrace were reported. Basal facets were thought to be the culprit in these events. The deep persistent slab is something to keep on your radar, especially with more weather in the forecast.

Snowpack Summary

Recently, the region has received up to 20 mm of rain and some new snow at high alpine elevations. The alpine and treeline has seen significant wind effect on all aspects including wind slab and wind pressed snow. Snow surfaces are highly variable and consist of rain crusts, moist snow and new dry storm snow at elevations above 1700 m. Below the surface sits a well-settled snowpack overlying several layers of interest. Down 70-100 cm you'll likely find a 5-10 cm thick crust which was buried on November 23 and in some areas, a feathery surface hoar layer down 50-60 cm producing moderate snowpack test results. The widespread crust/facet interface that was buried at the end of October can now be found 100-200 cm deep and exists region wide.

Problems

Loose Wet

An icon showing Loose Wet
With continued warming and light precipitation, I would expect loose wet avalanches to occur, especially on steep slopes and terrain features well into the alpine.
Be cautious of sluffing in steep terrain, particularly where the debris flows into terrain traps.Use extra caution on slopes if the snow is moist or wet.

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Possible - Likely

Expected Size

1 - 2

Storm Slabs

An icon showing Storm Slabs
Storm slabs may exist where the recent precipitation fell as snow. Watch for triggering in higher elevation, wind-exposed terrain.
Use ridges or ribs to avoid pockets of wind loaded snow.Be alert to conditions that change with elevation.

Aspects: All aspects.

Elevations: Alpine.

Likelihood

Possible - Likely

Expected Size

1 - 2

Deep Persistent Slabs

An icon showing Deep Persistent Slabs
Weak layers buried near the base of the snowpack can't be dismissed while new snow or rain load the surface. I'd limit my exposure to large overhead slopes, especially when the sun makes an appearance on Monday.
Take extra caution around areas with a thin or variable snowpack.Avoid areas with overhead hazard.

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Unlikely - Possible

Expected Size

2 - 3

Valid until: Dec 13th, 2017 2:00PM

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