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Avalanche Forecast

Archived

Dec 18th, 2018–Dec 19th, 2018

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 and human triggered avalanches likely.
Treeline
Natural avalanches possible, human triggered probable.
Below Treeline
Natural avalanches possible, human triggered probable.

Regions

North Columbia.

Slab development continues with more snow and wind. Choose conservative terrain as the new snow redistributes and settles.

Confidence

Moderate -

Weather Forecast

TUESDAY NIGHT: Flurries, accumulating 5-20 cm new snow.Moderate southwest wind. Freezing level 1000 m.WEDNESDAY: Flurries, 5-10 cm new snow.Moderate southwest wind. Freezing level around 1200 m.THURSDAY: Snow, accumulating 20-30 cm, increasing through the day. Moderate southwest wind gusting strong. Freezing level around 1300 m.FRIDAY: Cloudy with isolated flurries, up to 5 cm.Moderate west wind gusting strong. Freezing level dropping to valley bottom.

Avalanche Summary

Avalanche activity continues in the North Columbia region. On Friday, natural and explosives triggered avalanches up to size 3, and human triggered avalanches to size 2.5 were reported. Notably, several of these avalanches were triggered from a distance (remote triggered). On Saturday, explosives triggered avalanches to size 3.5, and natural and human triggered avalanches to size 2 were reported. Most recently, several natural avalanches to size 3.5 have been reported around the region.On Friday, a very large (size 3-4) natural avalanche was reported to have run full path, burying a road under several metres of debris on the west side of Kinbasket Lake. This avalanche occurred in the northern reaches of the North Columbia region, close to the boundary of the Cariboo region. These full path avalanches can catch people by surprise, especially when there is very little snow in the valley bottoms. A report of this avalanche can be found on the Mountain Information Network. here

Snowpack Summary

Up to 20 cm very recent snow brings storm totals to 60-100 cm over the last week or so. The storm snow buried a a weak layer of facets (sugary snow), surface hoar (feathery crystals), and a sun crust (on south facing slopes). Strong winds have promoted widespread slab formation, particularly with the most recent new snow available for transport.A weak layer from mid November is now buried up to 150 cm and consists of surface hoar and a sun crust. The potential may exist for smaller avalanches to step down and trigger this deeper layer, resulting in large avalanches. The most likely place for this layer to be a problem is on steep, south facing slopes at treeline where the surface hoar sits on the sun crust.At the base of the snowpack is a crust that formed in late October. Concern for this layer is dwindling but it may still be worth considering in places such as steep, rocky, alpine terrain, especially where the snowpack is shallow. It would likely take a large trigger such as a cornice fall to produce an avalanche on this layer.

Problems

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.

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.