Confidence
Fair - Timing, track, or intensity of incoming weather is uncertain for the entire period
Weather Forecast
Friday: Light snowfall (2-5cm through the day), becoming more intense on Friday night. Freezing level near valley floor, rising at night. Saturday: Moderate snow, perhaps 20cm. Freezing level gradually rising to around 1000m. Strong westerly winds.Sunday: Freezing level continuing to rise, peaking at 2000m. Moderate precipitation. Strong westerly winds. A cold front arrives on Sunday night.
Avalanche Summary
Avalanche activity has slowed down over the last two days, with only sporadic reports of avalanches. On Thursday, a cornice fall triggered a size 2 slab on a north aspect, which failed on the Feb 16. weakness. On Wednesday, numerous size 2-3 avalanches ran naturally, or with a remote trigger, on a variety of slopes. Most failed on an upper snowpack persistent weak layer. Natural avalanche activity is likely to increase again with this weekend's incoming weather.
Snowpack Summary
Down-flowing winds have created localized new wind slabs. Recent storm snow has become generally less reactive above the Feb 16. surface hoar layer and the early Feb. interface, however these layers are still exhibiting sudden planar ("pops") results in snowpack tests. The early Feb. interface consists of surface hoar (observed into the alpine, but most commonly found at and below treeline) and/or a crust (found on solar aspects, and on all aspects below about 1600m). These weaknesses are tricky to manage, as they are still touchy in certain locations, but the distribution of them is variable, so it's hard to know exactly which slopes are concealing these layers. Large cornices loom in some areas. Shallow snowpack areas may still harbour basal facets. The current snow surface is developing spotty surface hoar, surface faceting and sun crusts, which may bond poorly with incoming snow this weekend.
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.
Storm Slabs
Storm Slab avalanches are the release of a cohesive layer (a slab) of new snow that breaks within new snow or on the old snow surface. Storm-slabs typically last between a few hours and few days (following snowfall). Storm-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.