Dashboard Regions Weather Stations Radar Alerts Glossary
Contact About
Log In

Register for an account and never miss a forecast again!

Register

Avalanche Forecast

Archived

Jan 11th, 2018–Jan 12th, 2018

Alpine
Natural and human triggered avalanches likely.
Treeline
Natural and human triggered avalanches likely.
Below Treeline
Natural and human triggered avalanches likely.
Alpine
Natural and human triggered avalanches likely.
Treeline
Natural and human triggered avalanches likely.
Below Treeline
Natural and human triggered avalanches likely.
Alpine
Natural and human triggered avalanches likely.
Treeline
Natural and human triggered avalanches likely.
Below Treeline
Natural and human triggered avalanches likely.

Regions

Kootenay Boundary.

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.

Confidence

Moderate -

Weather Forecast

Friday: 3-7cm of the new snow / Light to moderate westerly winds / Freezing level at 700mSaturday: Mix of sun and cloud / Light westerly winds / Freezing level at 800mSunday: Mostly clear skies / Light southwest winds / Inversion with valley temperatures hovering around freezing and alpine temperatures reaching 2600m

Avalanche Summary

On Tuesday a widespread natural avalanche cycle to size 2.5 was reported from all aspects and elevations as the upper snowpack adjusted to a new load and increasingly warm temperatures.On Wednesday control work around Kootenay Pass produced very large avalanches to size 3.5 on southwest, south and southeast aspects. Natural avalanches ran to size 2.5 on southeast, east and northeast aspects. These avalanches may have started as storm slabs, but quickly 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. At the time of publishing this bulletin, no new avalanche activity had been reported, but I don't expect conditions to have improved to any significant extent.Looking forward, natural avalanche activity may taper-off somewhat; however, human triggering of large, destructive persistent slab avalanches at all elevation bands is expected to continue for the foreseeable future in many parts of the region.

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

Storm Slab avalanches are the release of a cohesive layer (a slab) of new snow that breaks within new snow or on the old snow surface. Storm-slabs typically last between a few hours and few days (following snowfall). Storm-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.