Regions
Northwest Inland.
Some thin new wind slabs are expected to develop with the forecast new snow. New snow is not expected to bond well to the old hard surface where surface hoar and/or facets exist.
Confidence
Fair - Timing, track, or intensity of incoming weather system is uncertain
Weather Forecast
Overnight and Wednesday: Overcast with moderate Westerly winds overnight and 3-5 cm of snow above about 700 metres. The freezing level is expected to continue to drop during the day as light flurries continue.Thursday: A few more cm of snow are forecast for the morning before the winds shift to the Northeast and colder arctic air enters the region.Friday: Mostly clear with moderate Northerly winds and freezing levels at valley bottoms. Alpine temperatures around -15.
Avalanche Summary
No new avalanches reported.
Snowpack Summary
The inversion broke down a little earlier than forecast in the interior, resulting in a solid melt-freeze crust that now has a layer of surface hoar above; even on southerly aspects. Forecast new snow amounts are only a couple of cm, so this layer may not get buried deep enough to persist through the next period of high pressure. If we get more snow than forecast expect the crust/surface hoar combination to be a very easy sliding layer. The deep persistent layer of weak facets continues to be a concern in shallow snowpack areas, however the re-frozen upper snowpack may make triggering less likely.
Problems
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.