Regions
Kootenay Boundary.
Solar radiation and daytime warming will be important in hazard assessment for the next few days, even on north slopes. Keep an eye out for large, mature cornices.
Confidence
Fair - Freezing levels are uncertain
Weather Forecast
Synopsis: A high pressure ridge will dominate the weather pattern for the next few days bringing warm temperatures and clear skies.Tonight: Clear with some cloudy periods, no precipitation, freezing level dropping to valley bottom. Ridge top winds light to moderate from the west.Wednesday: Sunny with cloudy periods, no precipitation in the forecast, freezing level rising to 1900m. winds from the south west, light to moderate.Thursday: Cloudy periods, possibility of flurries, freezing level around 1500m. Light to moderate ridge top winds. from the west possibly shifting north for a brief period.Friday: Cloudy with isolated flurries, trace of precipitation, freezing level around 1600m, light, locally moderate ridge top winds.
Avalanche Summary
We have reports of large natural avalanches occurring, most recently on north and north east aspects. A skier accidental size 2 around tree line yesterday indicates that even light loads may trigger a significant avalanche. 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 travel 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 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. 3 persistent weak layers are still 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.