Avalanche Forecast North Columbia

Sunday 3rd February 2019

Avalanche Danger Ratings Sun 3rd Feb 4:16PM 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 / light northeast winds / alpine low temperature near -20MONDAY - A mix of sun and cloud / northeast winds 10-30 km/h / alpine high temperature near -17TUESDAY - Mainly sunny / northeast winds 15-25 km/h / alpine high temperature near -15WEDNESDAY - A mix of sun and cloud / northwest winds, 15-35 km/h / alpine high temperature near -13

Avalanche Summary

Widespread avalanche activity continued on Saturday. Natural avalanches to size 3, explosives triggered avalanches to size 2.5, and human triggered avalanches to size 2 were reported. Several of the human triggered avalanches were triggered remotely and they failed on the mid January persistent weak layer.A widespread natural avalanche cycle to size 3.5, and explosives triggered avalanches to size 3.5 were reported on Friday, as were numerous human triggered avalanches to size 2. Many of these were remote triggered (triggered from a distance). Some of these avalanches failed within the new storm snow, but many of them reportedly failed on a persistent weak layer that was buried in mid January.Human triggered avalanches failing on the mid January persistent weak layer have been reported almost daily for the past two weeks in the North Columbia region.On Tuesday, in the neighboring Glacier National Park region, a human triggered size 3 avalanche occurred on a steep southeast facing slope in the alpine. There is a detailed report on the Mountain Information Network here

Snowpack Summary

The North Columbia region has received 30-90 cm of snow since Thursday. Average total amounts since Thursday are in the 50-70 cm range. This new snow sits on surface hoar (feathery crystals), facets (sugary snow), wind slabs and a crust on sun-exposed slopes.A persistent weak layer that was buried in mid January is now buried 50-100 cm. 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, and was very reactive during the height of the recent storm. It is uncertain how reactive this layer will be with temperatures dropping, but it may still be reactive to human triggers.

Wind Slabs Wind Slabs

Likelihood

Likely - Possible

Expected Size

1 - 2

30-90 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 shifting wind directions.

If triggered, wind slabs may step down to deeper layers and result in even larger avalanches.Be careful with wind loaded pockets, especially near ridge crests and roll-overs.

Aspects: All aspects.

Elevations: All elevations.

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Persistent Slabs Persistent Slabs

Likelihood

Likely - Possible

Expected Size

1.5 - 3

50-100 cm of snow is now sitting on a persistent weak layer of surface hoar and crust that was buried in mid January. This region has been the "hot spot" of activity on this layer, with more reactivity reported here than in neighboring regions.

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

Aspects: All aspects.

Elevations: Treeline, Below Treeline.

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