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Avalanche Forecast

Archived

Feb 3rd, 2019–Feb 4th, 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 unlikely, human triggered possible.
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

North Columbia.

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.

Problems

Wind Slabs

Wind Slab avalanches are the release of a cohesive layer of snow (a slab) formed by the wind. Wind typically transports snow from the upwind sides of terrain features and deposits snow on the downwind side. Wind slabs are often smooth and rounded and sometimes sound hollow, and can range from soft to hard. Wind 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.