New snow may not bond well to the older snow surface, especially where it's blown into dense pockets of wind slab.
Weather Forecast
Monday: Around 5 cm overnight then cloudy with sunny breaks and a chance of flurries. The freezing level rises to around 1500 m during the day. Ridge winds are moderate or strong from the W-NW, easing to light during the day. Tuesday: Increasing cloud with flurries developing. The freezing level jumps up to 1500 m and winds ease to light. Wednesday: Cloudy with sunny breaks and a chance of flurries. The freezing level is near 1600 m and winds are light.
Avalanche Summary
Recent avalanche activity has consisted mainly of loose wet sluffs on steep sun-exposed slopes during the day and natural or explosive-triggered cornice falls to size 2.5. On Saturday, explosive-triggered cornices did not release slabs below on north and east aspects in the alpine. Late last week there were a couple reports of failing cornices triggering slabs up to 60 cm deep on slopes below.
Snowpack Summary
A dusting of new snow overlies a melt-freeze crust on solar aspects and lower elevation terrain, and might be covering a layer of surface hoar on shady and sheltered slopes at treeline and in the alpine. Expect thin new wind slabs in exposed terrain. The surface hoar and/or crust layer buried in mid-February is now down 40-75cm. This layer was less reactive over the weekend with cooler temperatures. Large weak cornices have recently been a concern and have recently triggered persistent slabs on slopes below. The early January surface hoar/facet layer is typically down 70-120cm. Triggering an avalanche on this layer has become unlikely but it still has isolated potential to produce very large avalanches with a heavy trigger. In general, the lower snowpack is well settled and strong, apart from some thin snowpack areas where basal facets exist.
Problems
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.
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.