Regions
Northwest Inland.
Recent snowfall and strong winds are creating new problems. Solar inputs on Wednesday may elevate your local hazard. Assess the stability in your riding area before committing to avalanche terrain.
Confidence
Fair - Timing, track, or intensity of incoming weather system is uncertain
Weather Forecast
A ridge of high pressure should keep the NW Inland mainly dry on Wednesday. A mix of sun and cloud is expected with freezing levels at valley bottom and moderate alpine winds from the SW-W. On Thursday, sub-tropical moisture will mix with arctic air resulting in moderate snowfall. Freezing levels should remain at valley bottom and alpine winds will become strong-to-extreme. Conditions on Friday should be much the same with moderate-to-heavy snowfall, valley bottom freezing levels, and strong-to-extreme winds.
Avalanche Summary
On Monday, natural and human-triggered avalanches size 1 to 1.5 were reported in the south of the region. These were 20-30cm thick in sheltered areas and 30cm+ in wind loaded features. Sluffing from steep terrain was also reported. On Wednesday, natural avalanches are possible on sun exposed slopes or recently wind-loaded features. Skier-triggering is likely in wind loaded features and areas where the recent snowfall is settling into a cohesive slab.
Snowpack Summary
20-30cm of new snow has fallen in the last couple days. Strong winds have redistributed this snow in exposed terrain forming winds slabs in leeward features and stripping exposed slopes. The late-January crust is typically down 60-80cm in the south of the region and probably around half this depth in the north. Tests are indicating that this interface is generally well bonded but isolated avalanches have been reported to have released on this layer recently. The mid-January rain crust and/or surface hoar layer is down over 1m in the south and has generally become inactive. It may still be a concern in thinner snowpack areas, at higher elevations, and in the far north of the region. Near the base of the snowpack is a crust-facet combination buried in November. This deep persistent weakness was recently reactive and may still be touchy in the far north of the region. Wherever you are, I'd be cautious of this deep and potentially destructive layer. Possible triggers include thin spot triggering in high elevation terrain, a cornice fall, or a smaller avalanche stepping down.
Problems
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.
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.