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Avalanche Forecast

Archived

Apr 5th, 2014–Apr 6th, 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 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.

Regions

Cariboos.

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

Confidence

Fair - Forecast snowfall amounts are uncertain

Weather Forecast

Synopsis: A trough of moist air will push across the Province on Saturday and Sunday bringing clouds and precipitation.Tonight: 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 1400m, winds, light gusting moderate to strong from the southwest.Monday: Cloudy with light to locally moderate flurries, some parts of the region may see 25cm of precipitation. Freezing level around 2200m, winds moderate, gusting to strong from the south.Tuesday: Cloudy with flurries. Light to locally moderate precipitation amounts. Freezing levels remain high at around 2100 metres, winds generally light occasionally gusting to strong from the south west.

Avalanche Summary

Avalanche activity has slowed down considerably, but yesterday, 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. With incoming precipitation, strong winds and rising temperatures in the forecast, we expect avalanche activity to ramp up  on Sunday and early in the next week. There is real concern that persistent 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

Recent mild temperatures have contributed to a generally well-settled upper snow pack. Wind slabs have been forming in lee terrain on NW through E aspects at tree line and above as a result of moderate to strong upper level winds associated with the new snow.  Stability will decrease with daytime warming.Three persistent weaknesses to be aware of: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.