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Avalanche Forecast

Archived

Mar 13th, 2014–Mar 14th, 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 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

Kootenay Boundary.

The hazard may go up in the afternoon with daytime warming. For more insight into the current tricky snowpack, check out the most recent:Forecasters Blog.

Confidence

Fair - Forecast snowfall amounts are uncertain

Weather Forecast

Synopsis: The ridge of high pressure begins to break down with incoming Pacific frontal systems.Tonight: Clear periods, no precipitation in the forecast,  freezing level around 600 metres, ridge top winds light from the south west, occasionally gusting to strong.Friday: Cloudy, 5 to 10cm of precipitation, freezing level around 1400 metres, winds from the southwest , light to moderate, occasionally gusting to strong.Saturday: Cloudy with a trace of precipitation, freezing level around 1500 metres, ridge top winds moderate to strong from the south west.Sunday:  Cloudy, light to locally moderate precipitation, ( 5 to 15cm)  freezing level may climb to 1600 metres.

Avalanche Summary

We've received reports of large ( size 2 and 3 ) natural avalanches in the region. Cornice failures and resulting large avalanches are being reported in the Kootenay-Boundary region and in the neighboring areas as well. Careful attention to daytime warming and aspect will be necessary to ride safely in the back country.

Snowpack Summary

Warm temperatures have promoted rapid settlement of the recent storm snow into a dense slab that sits above a variety of old surfaces. Overnight freezing will help seal up the surface from the weak layers buried below, at least until warm daytime temperatures break down the surface crust, then all bets are off ! Rain up to 1900m has saturated the upper snowpack in some parts of the forecast area and will crust-over as the freezing level lowers at night. At elevations above the freezing level strong SW winds have have formed significant winds slabs in lee features adding load to the storm slab overlying a variety of persistent weak layers.3 persistent weak layers are buried in the snowpack, A January 28th layer of surface hoar, facets and crusts, a Feb.10th layer of surface hoar, facets and crusts now almost 200cm down,... and the March 2nd layer of surface hoar, facets and crusts at approximately 120cm from the surface.. Of these layers, the Feb. 10th/Jan. 28th layers still appear to be problematic with field reports indicating easy and sudden planar shears on this layer, especially on north aspects. Some parts of the forecast region recently received 5cm of new snow.

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.