Regions
Kootenay Boundary.
Heads up! Large avalanches have the potential to reach run-out zones. Be aware what, or who, may be above you.Special Avalanche Warning in effect for the interior ranges. Copy this address to view details: http://bit.ly/2nSOUyX
Weather Forecast
SUNDAY: Mix of sun and cloud. Ridge wind light to moderate, east. Temperature -10. Freezing level valley bottom.MONDAY: Mostly sunny. Ridge wind light, north. Temperature -8. Freezing level valley bottom.TUESDAY: Cloudy, light flurries. Accumulation trace. Ridge wind light to moderate, southwest. Temperature -8. Freezing level 800 m.
Avalanche Summary
There are no confirmed reports of avalanches from Friday, however is SAR responding in an incident involving a snowmobiler in the southern Slocan Valley that appears to be avalanche related.On Thursday, several large and destructive natural slab avalanches occurred through the region up to size 2.5 on all aspects and elevations. Avalanche control using explosives triggered numerous loose wet avalanches up to size 2 and a significant size 3 storm slab avalanche. These were reported from SE-SW slopes above 1900 m. Earlier in the week, two very large destructive avalanches up to size 3.5 were triggered remotely (from a distance) with crown depths up to 200 cm. At least one of these avalanches ran full-path, destroying mature trees.Natural avalanche activity will likely taper off through the weekend with colder temps; however, slopes will remain primed for human triggers.
Snowpack Summary
Storm snow accumulations from the past week vary from 10-45cm across the region at upper elevations. In the alpine this new snow has been redistributed to leeward slopes from strong northwest winds. Below 1800 m, up to 5 cm of low density snow covers a thin crust. This now brings 1- 2 m of settled snow sitting on three significant surface hoar/ crust layers that were formed early to mid-January, and back in December. Near the base of the snowpack a crust/ facet interface exists and will likely haunt us all season. These persistent weak layers that lurk within the snowpack are reactive, producing large and destructive avalanches. The snowpack is extremely complex and requires respect and diligence at this time.
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.
Persistent Slabs
Persistent Slab avalanches are the release of a cohesive layer of snow (a slab) in the middle to upper snowpack, when the bond to an underlying persistent weak layer breaks. Persistent layers include: surface hoar, depth hoar, near-surface facets, or faceted snow. Persistent weak layers can continue to produce avalanches for days, weeks or even months, making them especially dangerous and tricky. As additional snow and wind events build a thicker slab on top of the persistent weak layer, this avalanche problem may develop into a Deep Persistent Slab.