A Special Public Avalanche Warning is in effect for this region.
Weather Forecast
Temperatures start cooling on Saturday with the passage of a cold front. 5-10 mm precipitation is expected with the front overnight Friday/ Saturday, tapering to flurries on Sunday. The freezing level is around 2000 m on Saturday morning, falling towards 1500 m by the end of the day. Monday is dry and cool, with a chance of sun. Winds are light to moderate NW, easing to light by late Sunday.
Avalanche Summary
Skiers triggered a very large (size 3.5) persistent slab on Thursday on a NE aspect in the alpine in the Monashees. It failed on the late-Jan layer. Several large avalanches also failed naturally. Some failed in the recent storm snow, and some were glide crack releases and wet slabs gouging to ground. On Wednesday, a size 2.5 persistent slab failed on a steep shallow rocky feature at 2500 m, approximately 1 m deep. Cornices also collapsed naturally and with explosives over the last couple of days.
Snowpack Summary
More than a week of very warm temperatures has affected the snowpack by moistening upper snowpack layers to around 2300 m. There has been some ongoing reactivity of persistent slabs, perhaps due to warming altering the properties of the slab. Below treeline, the snowpack is probably trending isothermal (zero degrees throughout). In the alpine, wind affected surfaces can be found. Cornices may be large and weak. The late-Jan crust/surface hoar layer, buried up to a metre deep, remains a key concern. Triggering this could produce a surprisingly large avalanche. The mid-January surface hoar is typically down 80-120 cm and is most likely to be triggered from thin or rocky snowpack areas; or perhaps with a cornice fall, or an avalanche stepping down. The mid-December weak layer is down over 120cm, but is generally considered unreactive. As temperatures cool this weekend, conditions should gradually improve, but it's still a trouble-ridden snowpack adapting to change... so give it a bit of time.
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.