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Avalanche Forecast

Archived

Feb 2nd, 2019–Feb 3rd, 2019

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

Regions

South Columbia.

Natural avalanche activity has tapered off to some degree, but human triggered avalanches remain likely. Conservative terrain selection is recommended.

Confidence

Moderate -

Weather Forecast

SATURDAY NIGHT - Mainly cloudy with isolated flurries / southerly winds, 10-20 km/h / alpine low temperature near -12SUNDAY - Mainly cloudy with isolated flurries, 5-10 cm / southeast winds 10-25 km/h / alpine high temperature near -12MONDAY - A mix of sun and cloud / northeast winds 10 km/h / alpine high temperature near -16TUESDAY - Mainly sunny / northeast winds, 10-15 km/h / alpine high temperature near -12

Avalanche Summary

Avalanche activity continued on Saturday. Natural avalanches to size 3 and explosives triggered avalanches to size 2 were reported.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. A persistent weak layer that was buried in mid January is now buried 40-100cm. 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.

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.

Persistent Slabs

Persistent Slab avalanches are the release of a cohesive layer of snow (a slab) in the middle to upper snowpack, when the bond to an underlying persistent weak layer breaks. Persistent layers include: surface hoar, depth hoar, near-surface facets, or faceted snow. Persistent weak layers can continue to produce avalanches for days, weeks or even months, making them especially dangerous and tricky. As additional snow and wind events build a thicker slab on top of the persistent weak layer, this avalanche problem may develop into a Deep Persistent Slab.