Avalanche Forecast
Kootenay Boundary
A Special Public Avalanche Warning is in effect for this region.
Rapid warming on Sunday is expected to increase the likelihood of avalanches.
Avalanche Problem 1: Persistent Slabs
What Elevation?
Which Slopes?
Chances of Avalanches?
Expected Size?
Travel and Terrain Advice
- Avoid exposure to overhead avalanche terrain, large avalanches may reach the end of run out zones.
- Only the most simple non-avalanche terrain free of overhead hazard is appropriate at this time
Avalanche Problem 2: Storm Slabs
What Elevation?
Which Slopes?
Chances of Avalanches?
Expected Size?
40 to 80 cm of recent storm snow has settled into a reactive slab that rests on the early January weak layer. Large human-triggered storm slab avalanches remain likely, and may "step-down" to deeper, more destructive layers.
Travel and Terrain Advice
- The new snow will require several days to settle and stabilize.
- Storm slabs in motion may step down and produce large destructive avalanches.
- Avoid all avalanche terrain.
Avalanche Summary
On Wednesday control work around Kootenay Pass produced avalanches to size 3.5 on a variety of aspects. On the same day, natural avalanches failed to size 2.5. These avalanches may have started as storm slabs failing on the January 5th surface hoar, but stepped down to the mid-December and/or late November weak layers. An awesome MIN post from the same day also details some spooky skier-triggered avalanche activity around treeline in the Nelson area. Click here for details.
On Thursday, a skier remotely triggered a size 1.5 slab avalanche from a distance of 50 metres in the mountains north of Nelson. This avalanche, which failed on the January 5 surface hoar, shows how touchy this interface continues to be. Explosives control in the Kootenay Pass area continued to trigger persistent slab avalanches up to size 2.5.
On Friday, avalanche control work produced avalanches to size 2.
I expect reactivity to increase on Sunday in response to rapid warming.
Snowpack Summary
40 to 80 cm of recent snow is settling into a cohesive slab on top of the reactive January 5th interface which consists of a crust/surface hoar combination on steep southerly aspects and pure surface hoar on remaining aspects. The late December surface hoar also remains reactive and is now down 50 to 95 cm below the surface.
Adding to the complexity of the mid to upper snowpack is the mid-December surface hoar which is now 60 to 130 cm below the surface. This spooky interface continues to produce sudden snowpack test results and is most pronounced at treeline, but is also present below treeline. The overlying slab is now deep, dense and destructive.
Two laminated crusts created by rain events in late November lay just below the mid-December interface, and may co-exist with facets. In shallow, rocky terrain the mid-December surface hoar and the late November crust seem to be reacting together which is a volatile combination.
Weather Forecast
Sunday: Warm, dry and sunny. Freezing level rising to over 3000m. Cooler temperatures are expected to linger in the valleys below 1500 m. Light winds.
Monday: Pretty much a repeat of Sunday.
Tuesday. Clouds building through the day. Light rain turning to snow starting in the afternoon. Moderate southerly winds. Freezing level falling from 2500m in the morning to 1500 m in the afternoon.
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Our complex snowpack is currently producing very large and destructive avalanches on weak layers buried up to 130cm below the surface. Expert level knowledge and significant experience is required to venture into the backcountry at this time.