Avalanche Forecast South Columbia

Sunday 3rd February 2019

Avalanche Danger Ratings Sun 3rd Feb 4:13PM Danger Ratings Alpine: Considerable Danger Ratings Treeline: Considerable Danger Ratings Below Treeline: Considerable Wind Slabs Wind Slabs Persistent Slabs Persistent Slabs

Avalanche Canada Forecaster: kdevine

Date Issued:

Valid Until:

Human triggered avalanches remain likely, especially in wind loaded areas and at lower elevations where a buried surface hoar layer has produced avalanches recently.

Confidence

Moderate -

Weather Forecast

SUNDAY NIGHT - Mainly cloudy with isolated flurries, 2-4 cm / light northeast winds / alpine low temperature near -16MONDAY - Mainly cloudy with sunny periods / northeast winds 10-20 km/h / alpine high temperature near -14TUESDAY - Sunny with cloudy periods / northeast winds 15-25 km/h / alpine high temperature near -14WEDNESDAY - A mix of sun and cloud / northwest winds, 15-35 km/h / alpine high temperature near -12

Avalanche Summary

Widespread avalanche activity continued on Saturday. Natural avalanches to size 3, explosives triggered avalanches to size 2 and human triggered avalanches to size 2 were reported. Some of these failed within the new storm snow, but many of them reportedly failed on a persistent weak layer that was buried in mid January. Many of the human triggered avalanches were triggered remotely (from a distance).On Friday a widespread natural avalanche cycle to size 3, as well as numerous human triggered avalanches to size 2 were reported. Some of these failed within the new storm snow, but many of them reportedly failed on a persistent weak layer that was buried in mid January.On Tuesday, in the neighboring Glacier National Park region, a size 3 avalanche was skier triggered on a steep southeast facing slope in the alpine. More details and photos here.

Snowpack Summary

20-70 cm of new snow has fallen in the region since Thursday. The highest amounts fell in the northeast corner of the region: east of the Columbia (Upper Arrow Lake) and north of Trout Lake, with a few exceptions. This new snow sits on wind slab, surface hoar (feathery crystals), facets (sugary snow) and a crust on sun-exposed slopes. Recent strong to extreme winds have formed wind slabs at all elevations.A persistent weak layer that was buried in mid January is now buried 40-90cm. This layer consists primarily of surface hoar, however there is also a crust associated with it on sun-exposed slopes. This layer has been most reactive at treeline and below.

Wind Slabs Wind Slabs

Likelihood

Likely - Possible

Expected Size

1 - 2.5

20-70 cm of new snow has fallen in the region since Thursday. In many areas, recent winds have formed wind slabs at all elevations and on all aspects due to a shift in wind direction.

Avoid steep, unsupported slopes.If triggered, storm slabs may step down to deeper layers and result in even larger avalanches.

Aspects: All aspects.

Elevations: All elevations.

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Persistent Slabs Persistent Slabs

Likelihood

Likely - Possible

Expected Size

1.5 - 3

40-90 cm of snow sits above a weak layer of surface hoar (feathery crystals) and crust. This layer will likely be reactive due to recent snowfall.

Any steep opening in the trees should be treated as suspect right now.

Aspects: All aspects.

Elevations: Treeline, Below Treeline.

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