Avalanche Forecast

Fair - Timing or intensity of solar radiation is uncertain on Friday

Strong southerly winds combined with moderate snowfall are expected to continue until around midnight. The wind should clock to the west and lighten by morning as mostly clear skies show the sun for a couple of hours. Cloud and convective flurries with light southwest wind are forecast for the afternoon as the freezing level rises to about 900 metres. More cloud is expected to move in from the southwest in the morning on Saturday. The North Columbia may have scattered cloud until the afternoon when it is forecast to become overcast. The South Columbia and Purcell should cloud over by early morning. The south and west of the region could see up to 15cm and the north and east may get 5-10 cm on Saturday. Sunday may be mostly clear with only scattered clouds and light winds. Periods of strong solar radiation are possible.

Very large natural avalanches continued to be reported from Wednesday on a variety of aspects in the alpine; a size 4 natural avalanche occurred just to the north of the region initiating from an alpine start zone at 2500 m on a NE aspect. Experts considered this to be at least a 40 year event, and the slide pulled out mature timber. While not technically in the region, this event illustrates the magnitude of the avalanche problem in the region. On Monday, many natural avalanches occurred on all elevations in the Selkirks. Most were in the alpine, but some were also reported from treeline and below treeline elevations. In many cases, the failure layer was the mid-February surface hoar layer. Typical size was size 2, but several size 3 avalanches and one size 3.5 avalanche was reported, that set off a number of sympathetic avalanches on nearby features. In the Monashees, less activity was noted, with wind slab pockets reactive to human triggers up to size 1.5.

The region received about 20 more cm of new snow on Wednesday night/Thursday morning. This has brought the recent storm snow amount up to about 80 cm. Winds have been strong, mostly from the south or southwest with occasional easterly or southeasterly. This new snow covers old pencil hard wind slabs which were created by last week's strong W/SW winds. Storm snow remains easy to trigger. Persistent layers may still be sensitive to human triggering in areas where the snowpack goes from thick to thin, rock outcroppings being the classic example of this kind of structure. The big lurking danger remains the early February Surface Hoar that is now around 100 - 200cm deep. The snow above this weak layer has been under the influence of warmth and time which has settled the snow into a thick cohesive slab. Operators in the region have been diligently gathering data on this weak layer; in snowpack tests, the layer fails in a sudden planar fashion indicating that it has the potential to propagate across large distances. These tests mesh with the large avalanches that have been observed in the region recently. Conditions have been favorable for cornice growth recently, as a result many ridge lines are sporting large cornices.