South Columbia

Prolonged reactivity of storm slabs has earned them a persistent slab label, but the avoidance strategy hasn't changed. Keep it in mind as you navigate around the more obvious wind effect.

Moderate -

Tuesday: Mainly cloudy with isolated flurries and a trace of new snow. Light southwest winds. Freezing level to 1300 metres with alpine high temperatures around -8.Wednesday: Mainly cloudy. Light southwest winds. Freezing level to 1100 metres with alpine high temperatures around -9.Thursday: Cloudy with flurries bringing 6-10 cm of new snow, continuing overnight. Light southeast winds. Freezing level to 1300 metres with alpine high temperatures around -8.

Reports from Saturday included numerous observations of storm slabs releasing naturally as well as with skier traffic and explosives control. Sizes ranged from 2-3, with crown fracture depths varying from 30-100 cm. This activity occurred on all aspects but was focused at alpine elevations and this problem is now being identified as a 'persistent slab'. Wind slab releases made up a large number of observations, noted predominantly on southeast aspects.Widespread avalanche activity occurred in the top 30 cm of new snow on Friday. Numerous natural and skier triggered size 1 avalanches were reported, with the most reactive conditions on wind-affected slopes at treeline on north and east aspects.On Thursday, several size 1 skier triggered storm slab avalanches were reported. They were 30-50 cm thick and occurred on north and east aspects above treeline. One of the slabs subsequently triggered a larger size 2 avalanches that ran on the late-March crust. Some natural size 2-3 storm slabs avalanches were also reported in alpine terrain and a cornice fall on a north aspect in the Selkirks triggered a size 2.5 avalanche on an unidentified 2 m deep weak layer.

A variable 5-20 cm of new snow over Sunday night has brought storm snow totals from the past week to a wide-ranging 50-90 cm. with amounts that taper with elevation. The snowfall was initially accompanied by strong west wind and formed reactive slabs at higher elevations. More recent north winds reached extreme, so a mix of stubborn old and newer, more reactive wind slabs can now likely be found on a range of aspects. Below the wind effect at the surface, a break between storm pulses allowed for the formation of yet another layer of sun crust (south aspects) and surface hoar (shaded aspects) that is now buried by 20-30 cm of new snow. The full depth of recent storm snow sits on a persistent weak layer buried in late-March that consist of crusts below 1900 m and on south aspects, and surface hoar on shaded aspects at higher elevations.Pockets of surface hoar (buried mid-March) have been reported on shaded aspects at higher elevations and may be found approximately 70-100 cm below the surface.Deeper persistent weak layers from January and December are still being reported by professional observers, but are generally considered dormant.