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 -16THURSDAY - A mix of sun and cloud / west winds 10-20 km/h / alpine high temperature near -13FRIDAY - Mainly cloudy with flurries, 5-10 cm / south wind 15-30 km/h / alpine high temperature near -13SATURDAY - A mix of sun and cloud with isolated flurries / northwest winds, 10-15 km/h / alpine high temperature near -12
Avalanche Summary
On Wednesday, there was a report of several size 2 human triggered persistent slab avalanches. These were all triggered remotely (from a distance) and reportedly failed on a persistent weak layer that was buried mid January.On Tuesday, a few natural and human triggered wind slab avalanches to size 2 were reported, as well as loose dry avalanches to size 1.5.On Monday there were reports of several natural and human triggered avalanches to size 1.5. Several of these were triggered remotely (from a distance). Many of these avalanches were wind slabs, but several of them failed on a persistent weak layer that was buried in mid January. Numerous natural and human triggered avalanches up to size 2 were reported on Sunday. There were also two reports of persistent slab avalanches, one triggered by explosives and one occurred naturally. These were size 3 and 2.5 respectively and both occurred in the alpine on south and west aspects.
Snowpack Summary
15 to 40 cm of low density snow has fallen over the past week, with greater amounts in the south of the region. Recent northerly winds have formed wind slabs in lee areas. This snow is sitting on a surface hoar (feathery crystals) and crust layer that was buried on February 7th which could eventually develop into a problem layer.Two additional weak layers of surface hoar have produced large avalanches in the region over the past month. A layer buried at the end of January is around 40 cm deep and a layer buried mid-January is between 50 and 90 cm deep. The mid-January layer may also be associated with a crust on southerly aspects. These layers are most prominent at treeline and below. Human triggered avalanches continue to be reported on these weak layers.The remainder of the snowpack is considered generally strong. However, there have been sporadic reports of very large avalanches that have released near the base of the snowpack. Most of these avalanches have been in the high alpine. There has been about one report a week for the past month.
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.