Enjoy any sun that comes out, but be aware of its effect on the snowpack avoid exposure to sun-affected slopes. They may be far above you.
Confidence
Fair - Due to the number of field observations
Weather Forecast
Flurries taper out on Sunday. Freezing level is around 1400 m on Sunday, falling to valley floor overnight as a strong ridge sets up. It’s expected to get into a diurnal cycle after that (falling to valley floor at night and rising by day to around 1200 m). Monday and Tuesday are dry and cool, with a chance of sun. Winds are moderate NW, easing to light by late Sunday.
Avalanche Summary
Several size 1.5-2.5 avalanches were triggered naturally on Thursday and Friday in response to storm loading, wind and warm temperatures. A number of cornice collapses have been reported over the last few days. Loose wet avalanches failed naturally in steep terrain on Wednesday in response to warming. Also on Wednesday, explosives triggered a couple of size 2 slabs, which failed on the late-Jan crust. Human-triggering of the persistent slab remains possible.
Snowpack Summary
New snow may have been shifted into wind slabs on lee features at alpine and treeline elevations. Keep your eyes open for cornices, which may be large and unstable. A week or so of very warm temperatures has affected the snowpack, creating moist surface layers up to around 2000m. At low elevations, the snowpack may now be relatively uniform and starting to refreeze. The late-Jan crust/surface hoar layer, buried around a metre deep, remains a key concern, as it could still be human-triggered and could produce a destructive avalanche. The mid-January surface hoar is typically down 80-120cm and is unlikely to be triggered, apart from in a thin or rocky snowpack area. The mid-December weak layer is down over 120cm, but has been generally unreactive lately. Basal weaknesses remain in the back of operators' minds.
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.
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.