Avalanche Forecast

Issued: Jan 12th, 2018 4:25PM

The alpine rating is high, the treeline rating is high, and the below treeline rating is high. Known problems include Storm Slabs and Persistent Slabs.

Avalanche Canada jlammers, Avalanche Canada

A Special Public Avalanche Warning is in effect as large, destructive avalanches continue to fail throughout the region. Don't over-think the current avalanche scenario. Stick to extremely low angle terrain and avoid any overhead hazards.

Summary

Confidence

Moderate -

Weather Forecast

Saturday: Overcast with possible sunny breaks in the afternoon / Light and variable winds / Freezing level rising to 1500mSunday: Clear skies / Light and variable winds / Temperature inversion with valley temperatures remaining well below freezing and alpine temperatures reaching 2 degreesMonday: Clear skies / Light and variable winds / Temperature inversion with valley temperatures remaining well below freezing and alpine temperatures reaching 2 degrees

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.At the time of publishing this bulletin, no reports were available from Friday.Looking forward, human triggering of large, destructive persistent slab avalanches at all elevation bands will remain a real possibility for the foreseeable future in many parts of the region. Warming and solar radiation on Sunday, will likely ignite another round of destructive natural activity

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.

Problems

Storm Slabs

An icon showing Storm Slabs
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.
Avoid all avalanche terrain.Storm slabs in motion may step down and produce large destructive avalanches.The new snow will require several days to settle and stabilize.

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Likely

Expected Size

2 - 3

Persistent Slabs

An icon showing Persistent Slabs
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.
Only the most simple non-avalanche terrain free of overhead hazard is appropriate at this timeAvoid exposure to overhead avalanche terrain, large avalanches may reach the end of run out zones.

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Likely

Expected Size

2 - 4

Valid until: Jan 13th, 2018 2:00PM

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