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Avalanche Forecast

Archived

Apr 18th, 2014–Apr 19th, 2014

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

Regions

Kootenay Boundary.

Check out this Forecasters Blog post for more info on how to manage risk during the spring. Here's a quote: "resist the urge to rely on danger ratings alone". Conditions change rapidly at this time of year and you need to stay tuned in locally.

Confidence

Poor - Due to the number of field observations

Weather Forecast

Saturday: Cloudy with sunny breaks and a chance of showers or flurries. The freezing level rises to around 2000 m and ridge winds are moderate to strong from the S-SW. Sunday: A mix of sun and cloud. The freezing level is around 2000 m and ridge winds are moderate from the west.Monday: Cloudy with sunny breaks and a chance of showers. The freezing level jumps up to around 2600 m. Wind are moderate from the south.

Avalanche Summary

There are no reports of recent avalanche activity, but my guess is that this is due to the lack of reporters and not the lack of activity. Expect loose wet activity in steep terrain and the possibility of storm/wind slabs in higher terrain. Last Sunday there was a report of a size 2.5 natural deep persistent slab in the Rossland Range in response to strong solar radiation and warm temperatures. This avalanche released on a steep southeast aspect at around 2100 m and likely failed on the mid February weak layer. It's a good reminder of the potential for large deep avalanches under certain conditions.

Snowpack Summary

Considerably more snow than forecast fell on Thursday and into Friday. Some areas may have received 40+ cm of snow, with a snow line somewhere around 1500-1600 m. This new snow may not initially bond well to the underlying snow surface, which is probably a hard crust in many places. Moderate southwesterly winds have likely formed new wind slabs in exposed lee and cross-loaded terrain near ridge crests. The late January/early February persistent weak layer is deeply buried but could still wake up during periods of heavy precipitation (especially rain) or significant warming and solar radiation. Cornices are large in some areas and should be given a wide berth.

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.

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.

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.