Regions
Kootenay Boundary.
Warming temperatures and Solar radiation with play a leading role in the avalanche hazard in the coming days. Pay special attention to large ripe cornices !
Confidence
Fair - Timing or intensity of solar radiation is uncertain
Weather Forecast
Synopsis: An intense frontal system with subtropical moisture plowed it's way across the Province in the last 24 hours, pushing freezing levels above 2000 metres in some parts of the forecast area. The bulk of the moisture will be out of the forecast area later today.Tonight: Light to locally moderate precipitation in the forecast, freezing level should drop to 500m. Moderate to strong W winds.Monday: Mix of sun and clouds, possible flurries, light to moderate winds at ridge tops, freezing level may climb to around 1400m.Tuesday: Sunny with cloudy periods, no precipitation in the forecast, freezing around 1400m. winds from the west, light to moderate.Wednesday: Sunny with cloudy periods, freezing level rising to 1900m. Light ridge top winds.
Avalanche Summary
Rain, warm temperatures and additional loading from the recent storm, have produced numerous avalanches up to size 3. There are also reports of skier accidental and skier remote avalanches up to size 2. Many of these failed on the Feb.10 surface hoar / crust/ facet layers. There is ample opportunity now for a rider or skier to trigger an avalanche that might step down to any of the persistent weak layers in this years snow pack and produce a very large and destructive avalanche. Large cornices have been noted as a result of the high winds. As temperatures rise the chance of a cornice failure producing a large avalanche, will go up..
Snowpack Summary
The recent accumulation of up to 1 metre of storm snow is settling into a slab that now sits above a variety of old surfaces. There are buried facets on north aspects and sun crust on many south facing slopes. Rain up to 1800m has saturated the upper snowpack in some parts of the forecast area. At elevations above the freezing level strong SW winds have have formed winds labs in lee features. The surface snow has a "spongy" feel to it now, and there may be lighter snow underneath it making for "upside down" conditions, This will settle out with warm temperatures and time, improving skiing conditions. There are 3 persistent weak layers now buried in the snowpack, A January 28th layer of surface hoar, facets and crusts, a Feb.10th layer of surface hoar, facets and crusts, and the March 2nd layer of surface hoar, facets and crusts. Of these layers, the Feb. 10th layer appears to still be problematic, with field reports still indicating easy and sudden planar shears on this layer, especially on north aspects. The most recent weak layer, March 2nd, will be on the radar for a while as we wait for it to bond.
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.