Though avalanche activity has slowed down, it is worth keeping in mind that the potential still exists for humans to trigger persistent slab avalanches. While these avalanches are becoming less likely, the consequences remain high.
Weather Forecast
WEDNESDAY NIGHT - Mainly clear / northeast winds 10-20 km/h / alpine low temperature near -17THURSDAY - A mix of sun and cloud / west winds 10-20 km/h / alpine high temperature near -12FRIDAY - Mainly cloudy with flurries, 5 cm / south wind 15-35 km/h / alpine high temperature near -11SATURDAY - A mix of sun and cloud with isolated flurries / northeast winds, 10-15 km/h / alpine high temperature near -12
Avalanche Summary
On Tuesday, several natural, human and explosives triggered avalanches up to size 2 were reported in the region. Most of these were wind slabs, but one of the explosives triggered size 2 avalanches was a persistent slab avalanche on a north aspect at 2000.On Monday a few size 1-1.5 wind slab avalanches were reported, and some loose dry avalanches to size 1.5 were also reported. One notable report from Monday was of a size 2 natural persistent slab avalanche on a northeast aspect at 2000 m. This avalanche occurred on the persistent weak layer that was buried in January. Natural avalanche activity on this layer has mostly tapered off, so this came as a surprise to the observer.On Sunday, several natural and human triggered wind slab avalanches up to size 2 were reported. Several natural loose snow avalanches were reported on steep solar terrain, size 1.5-2.5.On Saturday, skiers triggered a few small (size 1) storm slabs and wind slabs as well as one larger (size 2) persistent slab avalanche. The persistent slab avalanche was triggered on a north aspect at 2100 m and failed on a 60 cm deep surface hoar layer.
Snowpack Summary
10-20 cm of recent snow has been blown into wind slabs in many areas. Recent variable wind directions means that wind slabs may be found on all aspects, mainly in the alpine and at treeline.There are two prominent weak layers in the upper snowpack. One was buried at the end of January and is approximately 40 cm below the surface. The deeper one was buried mid January and is approximately 75 cm below the surface. Both of these layers consist of a mix of surface hoar (feathery crystals) and facets (sugary snow), which may also sit on top of a sun crust on south facing slopes. Although avalanche activity on these layers has slowed down, test results indicate that humans could still trigger this layer in certain locations. These weak layers are most prominent at treeline and below treeline.Average snow depths are approximately 300 cm. Very sporadically, failures have occurred near the base of the snowpack in this region, or in neighboring regions. These releases have almost all been from high alpine areas, possibly triggered close to rocky features.
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.
Wind Slabs
Wind Slab avalanches are the release of a cohesive layer of snow (a slab) formed by the wind. Wind typically transports snow from the upwind sides of terrain features and deposits snow on the downwind side. Wind slabs are often smooth and rounded and sometimes sound hollow, and can range from soft to hard. Wind 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.