Warming temperatures have settled the recent storm snow into a cohesive slab sitting on weak facets (sugary snow) that is ripe for human triggers; intense solar radiation will increase the likelihood of human triggered avalanches.
Weather Forecast
FRIDAY NIGHT: Partly cloudy with some clearing / Light, westerly winds / Alpine low -10 / Freezing level below valley bottom.SATURDAY: Partly cloudy in morning becoming mostly sunny / Light, southwesterly winds / Alpine high 2 / Freezing level rising to 1800 m.SUNDAY: Sunny / Light, northwesterly winds / Alpine high 5 / Freezing level rising to 2200 m.MONDAY: Sunny / Light, westerly winds / Alpine high 7 / Freezing level rapidly rising to 3000 m.
Avalanche Summary
On Thursday, a few size 1 rider triggered persistent slab avalanches were reported on northerly aspects at treeline and below.On Wednesday, several naturally triggered, size 1.5 persistent slab avalanches and a few explosive triggered persistent slabs up to size 2.5 were reported on primarily north aspects at treeline and above. On Tuesday, there were reports of several human triggered persistent slab avalanches up to size 2. A few of these were triggered remotely (from a distance). There were also several reports of natural persistent slab avalanches up to size 3. These avalanches occurred on all aspects and at all elevation bands.
Snowpack Summary
10-15 cm of new snow brings the recent storm snow to 30-55 cm. This snow is sitting on facets (sugary snow), as well as surface hoar (feathery crystals) in sheltered areas and a crust on sun exposed slopes. At lower elevations, a weak layer buried in mid January can be found approximately 50-90 cm deep. This layer consists of surface hoar and facets, and may be combined with a crust on south facing slopes. This layer has been most reactive at lower elevations below treeline. Avalanche activity has dropped off significantly, however, the forecast warming event may awaken this layer in areas such as steep cutblocks.The lower snowpack is generally considered to be strong, except for shallow, rocky areas in the alpine.
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.
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.