Rising freezing levels over the weekend will increase the likelihood of large natural and human triggered avalanches. Avoid slopes with overhead exposure where falling cornices could trigger large avalanches
Weather Forecast
Another sunny day forecasted for Saturday but the big change is freezing levels rising to around 1900m. Cloudy skies are expected to return either Saturday evening or Sunday morning, but the exact timing of this is uncertain. If it's cloudy Saturday night, the hazard will increase on Sunday due to lack of "crust recovery". Freezing levels rise again on Sunday to around 2000m. Flurries are expected for Monday. Light to moderate southerly ridgetop winds are forecasted throughout the period.
Avalanche Summary
On Monday, 2 sledders were killed in an avalanche near Blue River. We still have very little information about the incident. More details will be made public as they become available. On Thursday, two natural size 3 slab avalanches were reported in the alpine. One on a north aspect and the other on a south aspect. Additionally, several small cornice failures triggered size 2 slab avalanches. Solar radiation and increasing freezing levels will become the driver for natural avalanche activity in the coming days.
Snowpack Summary
At ridgetop, cornices are huge and could become increasingly touchy with forecast solar radiation. Moderate westerly winds have created fresh wind slabs on top of old wind slabs on lee features at treeline and in the alpine. 70-100cm below the surface you'll find a persistent weak layer comprised of surface hoar, facets and/or a thick crust. This layer seems variably reactive. In other words, it's still really touchy in some places while in other spots it's really tough to trigger, and there's not much of a reliable pattern telling us what exact aspects are most suspect. I'd continue to be suspicious of steep, unsupported features at treeline and in the alpine as this layer has the potential for very large avalanches.
Problems
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.
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.