Snowfall amounts will be critical to determining hazard. More snow than forecast will make for a higher hazard.
Confidence
Fair - Forecast snowfall amounts are uncertain
Weather Forecast
Synopsis: A Pacific frontal system approaching the coast will spread clouds and light precipitation inland over the next few days.Thursday: Cloudy with flurries, some parts of the region may receive 10 to 15 cm of precipitation. No overnight freeze, freezing levels up to 1500m, Winds moderate, gusting to strong from the south west.Friday: Cloudy with flurries, parts of the forecast area may get 15 to 20 cm of precipitation. No overnight freeze and freezing levels may go up to 1600m. Winds light, gusting to moderate from the south west.Saturday: Cloudy with flurries. 5 to 10 cm of precipitation in the forecast for the region, daytime freezing level around 1700m, overnight freezing levels will drop close to valley bottom, winds, light to moderate from the south west.
Avalanche Summary
Reports of large avalanches were down from yesterday, but we are still getting reports of loose dry and loose wet avalanches from steep alpine terrain. One size 2 avalanche triggered by a cornice failure. Sluffing in steep terrain is being reported on all aspects.A low probability, but high consequence avalanche problem exists in the Columbia regions. Highly destructive and unpredictable avalanches are possible during these spring conditions. Smaller avalanches have been reported stepping down to old, deeply buried weak layers and producing very large avalanches.
Snowpack Summary
Recent warm temperatures have resulted in good settlement and bonding of the storm snow from earlier in the week. Reports of human-triggered avalanches have diminished. Three persistent weaknesses contribute to a highly variable snow pack with the possibility of triggering deeper instabilities. The mid-March sun crust/surface hoar layer down 50-80cm still has potential for human-triggering in isolated areas. The early-March crust/facet/surface hoar layer down around 80-120cm has become less susceptible to triggering by light loads, but still has the ability to produce large avalanches, we continue to hear reports of avalanches stepping down to this layer. The mid-February crust/facet/surface hoar layer is typically down at least 1.5m and direct triggering has become unlikely. However, large loads like cornices or smaller avalanches picking up mass might still trigger this layer and produce very large avalanches.
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.
Deep Persistent Slabs
Deep Persistent Slab avalanches are the release of a thick cohesive layer of hard snow (a slab), when the bond breaks between the slab and an underlying persistent weak layer deep in the snowpack. The most common persistent weak layers involved in deep, persistent slabs are depth hoar or facets surrounding a deeply buried crust. Deep Persistent Slabs are typically hard to trigger, are very destructive and dangerous due to the large mass of snow involved, and can persist for months once developed. They are often triggered from areas where the snow is shallow and weak, and are particularly difficult to forecast for and manage.