South Columbia

The South Columbias have been the bullseye for recent heavy snowfall. This means greater storm slab avalanche danger and greater potential for large storm slabs to step down to deeply buried weak layers.

Moderate - Forecast snowfall amounts are uncertain

Monday: Mainly cloudy with isolated flurries and a trace of new snow. Light northwest winds. Alpine high temperatures around -9.Tuesday: A mix of sun and cloud with cloud increasing and flurries beginning in the evening. Light northwest winds. Alpine high temperatures around -8.Wednesday: Cloudy with flurries bringing about 5 cm of new snow by the end of the day. Snowfall increasing overnight. Light southwest winds. Freezing level rising to a possible 1500 metres with alpine temperatures around -3.

Reports from Saturday included numerous natural storm slab releases from size 1.5-3 throughout the region. Activity was observed on all aspects and elevations, with high elevations proving the most active. Several very large persistent slabs were observed to have run naturally throughout the north and south Columbias. This MIN report details another remotely triggered persistent slab.Reports from Friday showed new storm slabs becoming touchy and producing numerous natural, remotely triggered, and ski cut releases generally from size 1-2.5. Crown depths ranged from 10-30 cm deep. One size 1.5 persistent slab was reported to have run on the mid January weak layer down about 100 cm.On Thursday, a size 2.5 persistent slab avalanche was triggered by a professional releasing a cornice onto a north facing slope at 1900 m. On Wednesday, Explosives control in the adjacent North Columbias yielded numerous persistent Slab results from size 2-3.5 on all aspects at all elevations. The deep mid-December layer and an even deeper layer from November were both frequent failure planes. The mid December layer is also suspected in two natural size 4 releases in and near the Glacier National Park area.

Another round of snowfall began on Sunday morning and 20 cm or more of new snow is expected to accumulate on the surface by Monday morning. This is adding to about a metre of recent storm snow which has settled into a slab (aided by recent wind and warming events) above the mid-January weak layer.Four active weak layers are now quite deep in our snowpack:1) About 80 to 150 cm of snow now sits on the crust and/or surface hoar layer from mid-January. The crust is reportedly widespread, with the possible exception of high elevation north aspects. The surface hoar is 5 to 20 mm in size and was reported at tree line elevations and possibly higher. This layer is the primary weak layer of concern in the South Columbias and remains well within the range of human triggering.2) Deeper in the snowpack, the early-January persistent weak layer is 130 to 175 cm below the surface. It is composed of surface hoar on sheltered slopes as well as sun crust on steep solar aspects and is found at all elevation bands. 3) Another weak layer buried in mid-December consisting of a facet/surface hoar/crust combination is buried up to 200 cm below the surface. It is most problematic at and below tree line.