Stormy weather continues to bring new snow, rain, and wind. Freezing levels are tricky to forecast, and overnight re-freeze are not certain.
Confidence
Moderate - Freezing levels are uncertain on Thursday
Weather Forecast
Overnight: Freezing level at 2200 metres, slowly dropping by morning to 1500 metres. Expect 5-10 mm of precipitation that will mostly be rain, except at the highest elevations, combined with strong southwest winds. Thursday: Daytime freezing level around 1500 metres, 3-5 cm of new snow in the alpine, and moderate westerly winds. Friday: Overnight freezing down to valley bottoms, and then rising up to at least 2200 metres. Mostly sunny with light southwest winds. Saturday: Freezing level remaining above 2000 metres, 5-10 mm of precipitation, combined with strong southwest winds.
Avalanche Summary
Wind slabs are expected to continue to develop in the alpine above the high freezing levels. At lower elevations, snow may be moist or wet and release easily in pockets of loose wet snow. The possibility of deep persistent avalanches continues during this period of warm and stormy weather. No new reports of avalanches.
Snowpack Summary
A warm, wet, and windy storm will form fresh wind slabs at higher elevations while rain will fall below treeline. March has delivered regular storms with roughly 50-90 cm of snow sitting above crust and facet interfaces from February. In some areas the snow above these interfaces may have a poor bond. The mid-pack in this region is generally strong, but the bottom third of the snowpack is composed of weak sugary facets roughly 1-1.5 metres deep. This remains a concern and should be on your radar, especially with the recent loading and ongoing warming.
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.
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.