Regions
Kootenay Boundary.
Confidence
Fair - Timing or intensity of solar radiation is uncertain on Tuesday
Weather Forecast
Overview: A ridge of high pressure will bring dry conditions to the region on Tuesday. A frontal system will bring moderate snowfall on Wednesday before the dry ridge rebuilds on Thursday.Tuesday: Generally clear skies / Light to moderate northwest winds / Freezing level at 1500mWednesday: 15-25cm of snow / Moderate to strong southwest winds / Freezing level at 1400mThursday: Mix of sun and cloud with light flurries / Moderate northwest winds / Freezing level at 700m
Avalanche Summary
Although observations were extremely limited, several natural size 1-1.5 loose wet avalanches were observed on Sunday. They occurred in response to steady rain at lower elevations. Looking forward, solar radiation may be the driver for natural avalanche activity on Tuesday.
Snowpack Summary
Variable amounts of recent storm snow was blown by strong winds into much deeper deposits in lee terrain. These recent accumulations overlie crusts on previously sun-exposed slopes and surface hoar in shaded terrain. Rain at lower elevations continued to saturate the snowpack. If the air temperature dips below freezing, lower elevation surfaces may exist as a refrozen crust.Below the new snow, 60-100cm of settled snow has been bonding poorly to buried surface hoar and crusts. The deeper facet/crust persistent weakness buried at the beginning of February, now down 60 to 160cm, has been highly variable in terms of reactivity and is still very difficult to trust. Needless to say, any avalanche at these deeper, persistent interfaces would be large and destructive.Weak basal facets exist in many areas, but without a large load, triggering now is unlikely.
Problems
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.
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.