Regions
Northwest Inland.
Recently formed storm and wind slabs will continue to be reactive to human-triggering on Thursday and conservative terrain selection remain critical.Use extra caution on south facing slopes in the afternoon if the sun is out in full force.
Confidence
Moderate - Timing, track, or intensity of incoming weather system is uncertain
Weather Forecast
3-10cm of snowfall is expected Wednesday overnight throughout most of the region. On Thursday, most of the region should see dry conditions with a mix of sun and cloud. Freezing levels are expected to be around 1000m and should fall to valley bottom overnight. Alpine winds are forecast to be light from the west. Friday is expected be mainly dry and cloudy but light flurries and sunny breaks are both possible. Afternoon freezing levels are expected to reach 700-900m and alpine winds should be light from the southeast. The next organized storm system is forecast to hit the north coast Friday night and 5- 15cm is currently being forecast to reach the inland region.
Avalanche Summary
On Tuesday, a size 1 storm slab was ski cut on a convex roll at treeline. On Monday, isolated wind slab avalanches up to size 1.5 were reported. On Sunday, a ski cut produced a size 1 storm slab avalanche on an east aspect at 1400m elevation. The slab was 25cm thick. A small natural cycle was reported on Sunday up to size 2 and failing in the recent storm snow, mainly in the alpine. Recently formed storm and wind slabs are expected to remain reactive to human-triggering on Thursday. If the sun comes out, natural avalanches are possible on steep south facing terrain features. In the far north, deeply buried persistent weak layers may still be reactive to large triggers such as a small avalanche stepping down or a cornice failure.
Snowpack Summary
40-80cm of snow has accumulated over the past week and overlies a melt freeze crust which extends up to around 2000m elevation. This recent snow is reported to be bonding well to the crust. Moist snow was reported below 1100m on Tuesday and wet snow below 800m. Recent wind has redistributed the surface snow at higher elevations forming wind slabs in leeward features. The early January surface hoar/facet layer is down around 1m+ and remains a concern for commercial operations. This layer seems the most reactive in the north of the region but may still be a concern in the south as well. Shallow snowpack areas in the east and north of the region may have a weak base layer of facetted snow on or just above the ground.
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.
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.