The snowpack still hasn't adjusted to spring weather at high elevations. Keep your guard up and an eye on overhead hazards while persistent slab problems are still in play.
Weather Forecast
Saturday night: Scattered flurries bringing up to 5 cm of new snow. Light southwest winds.Sunday: A mix of sun and cloud with scattered flurries and about 5 cm of new snow. Light west winds. Freezing level to 1400 metres with alpine temperatures around -7.Monday: A mix of sun and cloud. Light northwest winds. Freezing level to 1500 metres with alpine temperatures around -6.Tuesday: Cloudy with sunny periods. Light southeast winds. Freezing level to 1800 metres with alpine temperatures around -4.
Avalanche Summary
Reports from Friday showed several deep persistent slab releases to Size 3.5 having occurred within the previous 24 hours with natural, cornice fall, and rider triggers. One of these featured a crown fracture of up to 3 metres in depth. Numerous wind slabs were also observed releasing naturally to Size 2.5 while natural loose wet and loose dry slides ranged from Size 1.5-2.Reports from Thursday include numerous observations of storm slabs releasing naturally from Size 1-2.5 throughout the region. Natural triggers (including natural cornice fall) featured prominently in reports. Crown fractures generally ranged from 30-40 cm and northeast to northwest aspects were the most active.On Wednesday, numerous storm slabs up to Size 2.5 were observed. Several Size 1 storm and wind slabs were also reactive to rider triggering.
Snowpack Summary
About 10 cm of new snow fell over Friday night and Saturday morning, burying a temperature crust at about 1900 metres and below as well as sun crust all the way into the alpine on most solar aspects. The new snow brings recent storm snow totals at upper elevations to 40-60 cm. This storm snow is dry up high and moist at 1800 m and below. 90-130 cm of accumulated snow now overlies a rain crust below 2000 m and sun crust on solar aspects at higher elevations. New wind slabs are developing on leeward slopes and behind terrain features and large, fragile cornices exist along ridgelines. At higher elevations, the February weak layers are down 150-190 cm and woke up during last week's storm with many avalanches stepping down to them. The deep mid-December facet layer and November rain crust both still linger near the bottom of the snowpack and a few avalanches and cornice falls have also stepped down to these layers last week resulting in some very large full depth avalanches. These layers remain a real concern while touchier wind slabs and cornices continue to present the risk of acting as a trigger for deeper weaknesses.
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.
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.