Avalanche Forecast

Moderate - Timing or intensity of solar radiation is uncertain

Another 5-15 mm of precipitation is expected Wednesday overnight before conditions dry out on Thursday morning. Freezing levels are expected to remain around 2000 m overnight and are forecast to drop below 1500 m on Thursday morning. Alpine wind is expected to be strong from the southwest overnight and ease to light by Thursday afternoon. During the day on Thursday, a mix of sun and cloud is expected with the possibility of isolated flurries. A mix of sun and cloud is expected on Friday with light alpine wind. Freezing levels are expected to drop to valley bottom early Friday morning and reach around 1600 m in the afternoon. The next storm system is expected to arrive Friday night and should persist until Sunday morning. Models are currently showing 20-40 mm of precipitation from the storm with freezing levels reaching around 2000 m on Saturday afternoon.

An early report from Wednesday includes a natural size 3 cornice triggered avalanche and a natural size 3 wet slab avalanche at 2200-2400 m elevation. On Tuesday, natural avalanche activity was reported in many parts of the region. Most of this activity was wet slabs up to size 3 and loose wet avalanches up to size 2 in response to the high elevation rain. A natural size 2.5 persistent slab avalanche was also observed on an east and southeast aspect slope at 2200 m in the area south of Nelson which failed on a layer down 50 cm. Ski cutting on Tuesday morning triggered several storm slab up to size 1.5 and explosives triggered numerous wet slab avalanches up to size 2.5 in the afternoon. On Thursday, if the sun comes out in full force, it will further destabilize an already warm snowpack. Natural loose wet and wet slab avalanches remain possible on steep sun exposed slopes. Large persistent slab avalanches also remain a serious concern until the snowpack has time to recover from the recent rain and warming. In the high alpine, recent storm snow will remain touchy and may fail naturally with solar triggers.

On Tuesday and Wednesday, freezing levels reached 2200 m or higher. A report from Tuesday suggested the snow surface was moist above 2000 m and wet below 2000 m. A report from Wednesday says the rain has penetrated up to 40 cm deep into the snowpack. As temperatures drop on Thursday, a widespread crust layer is expected to form on the surface. The exception to this will likely be sun exposed slopes where solar radiation is expected to continue to destabilize the snowpack.The late-February interface is now down 70-120 cm. This layer is composed of sun crust, surface hoar, and weak faceted snow and was producing easy, sudden results in snowpack tests in observation prior to the rain event. The thick mid-February crust layer is now down 90-135 cm and exists on solar aspects and at lower elevations. This layer had gone dormant but will be tested during this storm. In most deeper snowpack areas, the snowpack is generally well settled and stable below this crust layer. However, some areas have a lingering basal weakness at the bottom of the snowpack. This is especially prevalent in shallow snowpack areas of the region.