Avalanche Forecast

Archived

Dec 11th, 2014–Dec 12th, 2014

Alpine

Natural avalanches possible, human triggered probable.

Treeline

Natural avalanches possible, human triggered probable.

Below Treeline

Natural avalanches unlikely, human triggered possible.

Alpine

Natural avalanches unlikely, human triggered possible.

Treeline

Natural avalanches unlikely, human triggered possible.

Below Treeline

Natural avalanches unlikely.

Alpine

Natural avalanches unlikely, human triggered possible.

Treeline

Natural avalanches unlikely, human triggered possible.

Below Treeline

Natural avalanches unlikely.

Regions

Cariboos.

Although the trend shows improvement remember that the potential for triggering an avalanche is greatest at higher elevations due to recent heavy snowfall and strong winds.

Confidence

Fair - Due to the number of field observations

Weather Forecast

One last system is expected to cross the province tonight bringing moderate precipitation, high winds, and maintaining high freezing levels. We could see 10-20 cm on Friday. Freezing levels start near 1800 m but should drop to 1500 m late in the day. Winds are strong from the South-Southwest easing to light from the Northwest. The weekend looks much drier with a mix of sun and cloud. Freezing levels around 800-1000 m on Saturday and valley bottom on Sunday. Winds remain light.

Avalanche Summary

A widespread natural avalanche cycle with slides up to size 3.5 was reported south of Valemount on Thursday. Large slab avalanches were observed above 2000 m and numerous wet slides were observed at lower elevations in steep terrain. Similar activity was likely in other parts of the region.

Snowpack Summary

The storm snow is expected to be wet up to around 2000 m and moist up to around 2400 m. Below the old storm snow (15-30cm) is a weak layer of surface hoar. Reports from the region suggest that anywhere from 50-150 cm of settling snow overlies one or more weak layers which formed during November. Snowpack tests suggest that these weak layers are getting harder to trigger but still have the potential to produce large avalanches if triggered. Recent strong winds and warm temperatures have likely created deep and dense wind slabs in lee features in exposed alpine terrain.

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.

Loose Wet

Loose Wet avalanches are the release of wet unconsolidated snow or slush. These avalanches typically occur within layers of wet snow near the surface of the snowpack, but they may quickly gouge into lower snowpack layers. Like Loose Dry Avalanches, they start at a point and entrain snow as they move downhill, forming a fan-shaped avalanche. Other names for loose-wet avalanches include point-release avalanches or sluffs. Loose Wet avalanches can trigger slab avalanches that break into deeper snow layers.