Regions
Kootenay Boundary.
Intense solar radiation is expected to keep avalanche danger elevated tomorrow. Continued natural avalanche activity is possible.
Confidence
Moderate - Timing or intensity of solar radiation is uncertain on Friday
Weather Forecast
FRIDAY: Mainly sunny and dry with freezing levels back up to 1800m. Clouds are expected to roll back in early afternoon and winds should remain light to moderate southeasterly to southwesterly. SATURDAY Mainly cloudy with snow flurries bringing another 5-15cm. Freezing levels hovering around 1800m and moderate to strong southwesterly ridgetop winds. SUNDAY: A mix of sun and cloud, with light flurries. Freezing levels dropping back down to 1700m and moderate to strong southwesterly ridgetop winds.
Avalanche Summary
Reports from Wednesday include isolated harmless skier-triggered storm slab avalanches and one natural Size 1.5 on a northeast aspect at 2150m. Of note was a 50-60cm deep Size 1.5 persistent slab avalanche running on the late February surface hoar, which was ski-cut from the top of a ridge into a steep north facing chute. It propagate the full width of the chute and ran to the bottom. Initial reports from Thursday include several natural and explosives controlled Size 1.5-2 storm slab avalanches. Widespread natural avalanche activity is likely in response to heavy loading from snow, wind and rain.
Snowpack Summary
Another 15-25cm adds to the 35cm of recent snow that is bonding poorly to a widespread rain crust which extends into alpine elevations. A persistent weak layer buried late-February is now likely down 50-80cm and may still be sensitive to human triggers as indicated by recent avalanche activity and hard but sudden snowpack test results. This weakness is widespread buried surface hoar on sheltered slopes above 1700m, and a crust potentially with associated facets on previously sun-exposed slopes (primarily south aspects). Over a metre down you will likely find the mid-February crust/facet/surface hoar layer, which has been inactive lately.
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.
Persistent Slabs
Persistent Slab avalanches are the release of a cohesive layer of snow (a slab) in the middle to upper snowpack, when the bond to an underlying persistent weak layer breaks. Persistent layers include: surface hoar, depth hoar, near-surface facets, or faceted snow. Persistent weak layers can continue to produce avalanches for days, weeks or even months, making them especially dangerous and tricky. As additional snow and wind events build a thicker slab on top of the persistent weak layer, this avalanche problem may develop into a Deep Persistent Slab.