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Avalanche Forecast

Archived

Apr 4th, 2014–Apr 5th, 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 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 possible, human triggered probable.

Regions

Cariboos.

New snow amounts and rising temperatures are driving the hazard these days. Cornices will become weak as temperatures rise.Fore more insight into the current hazard problems, check out the latest Forecasters Blog.

Confidence

Fair - Forecast snowfall amounts are uncertain

Weather Forecast

Synopsis: Slow moving frontal systems are bringing precipitation into the interior of BC for the next few days.Tonight: Cloudy with flurries, trace of precipitation possible. Freezing level should drop to near valley bottom. Winds light, gusting to moderate from the south west.Saturday: Cloudy with flurries. 5 to 10cm precipitation in the forecast for the region, daytime freezing level around 1500m, winds moderate from the south west.Sunday: Cloudy with flurries. Trace of precipitation, for the region, freezing levels around 1300m, winds, light gusting moderate to strong.Monday: Cloudy with light to locally moderate flurries, some parts of the region may see 20cm of precipitation. Freezing level around 2200m, winds moderate, gusting to strong from the south.

Avalanche Summary

No reports of avalanche activity yesterday, but  today (Friday) a commercial operator reported a size 3.5 natural avalanche, on a north aspect, initiating near ridge top in recent storm snow, then stepping down to the Oct./Nov. basal facets and running full path. There is concern that weak layers will become more reactive with rising temperatures and solar warming. This spring, a low probability, high consequence avalanche problem plagues the Columbia regions. Highly destructive and largely unpredictable avalanches are possible right now.

Snowpack Summary

Convective squalls have produced 5 to 10 cm in the last few days throughout the forecast region. Suncrust from the last clear sunny days, has been buried by convective snow squall activity. Wind slabs still exist (and may be building) in lee terrain on NW through E aspects at tree line and above.Three persistent weaknesses now contribute to a highly variable, complex snowpack.A mid-March sun crust/surface hoar layer down 50-80cm has potential for human-triggering in select locations( New wind slabs have been formed on this layer).An early-March crust/facet/surface hoar layer down around 80-120cm has become less susceptible to human-triggers, but still has the potential to produce large avalanches. We've received recent reports of avalanches stepping down to this layer. A mid-February crust/facet/surface hoar layer that we've been watching is now down around 1.5m and still producing sudden planar shears in snow pit tests. Although direct triggering of this weak layer has become less likely, a large load like a cornice failure or smaller avalanches gaining mass could trigger this layer and produce very a large and destructive avalanche.

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.