Moderate winds and new snow are expected to form new wind slabs on Monday. Use extra caution as you transition into wind affected terrain.
Confidence
Moderate - Intensity of incoming weather systems is uncertain on Monday
Weather Forecast
The next low pressure system arrives on the south coast on Sunday evening. 10-20 cm of new snow is expected Sunday overnight with another 5-10 cm during day on Monday. Alpine wind is forecast to be moderate from the south and southwest. Freezing levels are forecast to be around 800 m overnight and reach around 1200 m in the afternoon. A mix of sun and cloud is currently expected on both Tuesday and Wednesday with the possibility of lingering flurries on Tuesday. Alpine wind is forecast to be light to moderate on Tuesday and light on Wednesday. Afternoon freezing levels are forecast to peak around 800 m on both days.
Avalanche Summary
On Saturday, explosives released two large cornices which did not trigger slabs on the slopes below. On Friday, reports of natural activity were limited to one size 2 wet slab at around 1900 m elevation. Explosives triggered a couple size 2 cornices and one size 1.5 storm slab which was 20 cm thick. On Thursday, a few natural storm slabs up to size 3 were observed and explosives triggered a few size 2 storm slabs which were typically around 60 cm thick. On Monday, new wind slabs are expected to develop in exposed high elevation terrain. Large cornices which developed last week may still be weak and could fail under the weight of a person.
Snowpack Summary
At higher elevations, 20-30 cm of recent snow overlies the widespread mid-February melt-freeze crust, which extends as high as 2200 m and is up to 15 cm thick at treeline. The recent storm snow is reported to be bonding well to the crust. In the alpine, wind slabs and cornices were being reported on northerly aspects. Below around 2000 m, the crust is at or near the surface of the snowpack and is reported to be supportive to the weight of skier.
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.