A Special Public Avalanche Warning remains in effect Sunday. The freezing level remains quite high (2600 m) which will keep danger ratings elevated.
Confidence
Moderate - Freezing levels are uncertain on Monday
Weather Forecast
Temperatures are expected to remain warm Sunday before beginning to cool Monday as a weak Pacific front injects cooler and cloudier marine air into the region. SUNDAY: Freezing level starting near 2400 m, climbing to 2600 m, light west/southwest wind, no significant precipitation expected, increasing cloud cover throughout the day. MONDAY: Freezing level beginning near 2500 m, lowering throughout the day to around 1900 m by sunset, light to moderate southwest winds, 2 to 6 mm of precipitation expected, overcast skies. TUESDAY: Freezing level beginning near 1500 m rising to around 2000 m, broken cloud cover, light to moderate wind generally out of the west, isolated convective snow/rain flurries/showers possible. For more detailed mountain weather information visit avalanche.ca/weather
Avalanche Summary
Lot's of activity to report from Friday. Wet loose and wet slab avalanches failed naturally resulting in avalanches to size 3. Glide crack failures to size 3 were also observed. Loose wet avalanches to size 2 running on the ground were reported from the south of the region. On Thursday, solar radiation continued to result in natural cornice falls up to size 2.5 and loose wet avalanches up to size 2.0. On Wednesday, slab and loose snow avalanches were reported up to size 2 on a variety of aspects, mostly triggered by cornices or solar radiation. On Tuesday numerous loose wet avalanches up to size 2.0 were reported, and one of these loose wet slides stepped down to a buried crust down 50 cm and resulted in a size 2.5 on a steep east aspect at 2200 metres.
Snowpack Summary
Ongoing warm daytime temperatures combined with mild nights continue to destabilized the upper snowpack. On Sunday, any surface crust is expected to break down early, and persistent weak layers may fail if the warming reaches their fragile structure. The late February surface hoar/crust layer is down 40-90 cm. This layer may continue to react to human triggers during high daytime temperatures. Loose wet avalanches in motion, or cornice failure could result in an avalanche that steps down to deeply buried weak layers. Cornices continue to be described as large and fragile, and may fail with continued warming. Conservative terrain without overhead hazard is a good strategy for avoiding the persistent slab problem.
Problems
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.
Cornices
Cornice Fall is the release of an overhanging mass of snow that forms as the wind moves snow over a sharp terrain feature, such as a ridge, and deposits snow on the downwind (leeward) side. Cornices range in size from small wind drifts of soft snow to large overhangs of hard snow that are 30 feet (10 meters) or taller. They can break off the terrain suddenly and pull back onto the ridge top and catch people by surprise even on the flat ground above the slope. Even small cornices can have enough mass to be destructive and deadly. Cornice Fall can entrain loose surface snow or trigger slab avalanches.
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.