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Avalanche Forecast

Archived

Dec 29th, 2013–Dec 30th, 2013

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

Regions

Cariboos.

Confidence

Poor - Intensity of incoming weather systems is uncertain

Weather Forecast

Tonight and Monday: Periods of snow, heaviest on the western slopes – 15-25 cm. The freezing level is near valley bottom and winds are moderate to strong from the W-NW. Tuesday: Cloudy with possible sunny breaks and a chance of flurries. The freezing level is near valley bottom. Winds are light to moderate from the NW.Wednesday: A mix of sun and clouds with light snow possible late in the day. The freezing level is at valley bottom.

Avalanche Summary

Several snowmobile triggered slab avalanches up to size 2 were reported in the Cariboos near Valemount. Most of these involved the most recent storm snow, but it's possible a couple larger events stepped down to deeper persistent weaknesses. Also, a few natural size 2-3 slab avalanches were reported on Saturday from steep NW-NE aspects in the alpine in other areas. One event (size 3) appeared to fail on a deeper persistent weakness in the snowpack. Similar activity is expected to continue with additional loading from snow and wind on Sunday and Monday.

Snowpack Summary

Another 10-15 cm of snow fell on Saturday night bring storm totals to around 50 cm in some areas. Winds have been generally moderate to strong from the SW-NW and temperatures have fluctuated. Expect to find touchy wind slabs in exposed lee terrain at and above treeline, and buried rain crusts below 1600 m. A couple buried weak layers (surface hoar or facets) are now down 80-100 cm deep. Recent snowpack test results on these layers vary, but some are showing this layer "pop" with easy to medium loads, indicating a potential for human triggering.Snowpack depths vary, but in general 150 cm of snow can be found at treeline, with 100-200 cm in the alpine. In many places we're still dealing with a relatively thin snowpack (thanks to a windy early season) so there's not a whole lot of snow between riders and the sugary snow (facets) near the ground. The basal facet/crust combo has been recently active in parts of the region and continues to give easy to moderate results in snowpack tests.

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.

Deep Persistent Slabs

Deep Persistent Slab avalanches are the release of a thick cohesive layer of hard snow (a slab), when the bond breaks between the slab and an underlying persistent weak layer deep in the snowpack. The most common persistent weak layers involved in deep, persistent slabs are depth hoar or facets surrounding a deeply buried crust. Deep Persistent Slabs are typically hard to trigger, are very destructive and dangerous due to the large mass of snow involved, and can persist for months once developed. They are often triggered from areas where the snow is shallow and weak, and are particularly difficult to forecast for and manage.