Avalanche forecast

Kootenay Boundary

Feb 24 – 25, 2013Avalanche Canada
View on map
Archived · expired 14 years ago

Avalanche danger

Tue
Wed
Alpine
4 · High
Treeline
4 · High
Below
3 · Considerable
Open full map

Highlights

Avalanche problems

  • Persistent Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Likely
    Size
    1–6
    The presence of weak layers buried in the upper snowpack means there is a risk of triggering surprisingly large slabs.

  • Storm Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Likely - Very Likely
    Size
    1–5
    Loading from new snow and wind has increased the avalanche danger, especially where the wind has shifted snow into slabs behind terrain breaks like ridges and ribs.

Confidence

Poor - Timing, track, or intensity of incoming weather is uncertain for the entire period

Weather Forecast

Sunday night: 15-30 cm snow. Strong SW winds. Alpine temperature around -7.Monday: 5-15 cm snow. Light to moderate NW winds. Alpine temperature around -5.Tuesday: No snow. Sunny breaks. Light SW winds. Alpine temperature around -6.Wednesday: Light snow. Light SW winds. Alpine temperature around -10.

Avalanche Summary

A natural cycle began on Friday and continued on Saturday, with several slabs to size 2.5 failing on all aspects. Many were triggered by wind-loading. They failed within the storm snow or on the mid-Feb surface hoar or crust layers. Explosives triggered several size 2-3 slabs, failing on the same interfaces. A couple of cornice falls also triggered large slabs on slopes below. I'm expecting the next avalanche cycle to occur on Sunday night/Monday in response to new snow and wind, but with poor confidence in the weather forecast.

Snowpack Summary

In much of the region, up to 55 cm recent snow overlies weak interfaces buried in mid-February (mainly surface hoar/ sun crust layers). The storm slab above these interfaces has the potential for wide propagations and surprisingly large avalanches, especially where winds have shifted the snow into slabs in the lee of terrain breaks. A thin freezing rain/rime crust formed on Friday, which is now buried by about 15 cm snow. Snow forecast overnight Sunday and on Monday will add to these storm slabs.In the Rossland Range, surface hoar which was buried mid-week is 20-30 cm down and exhibits easy, sudden results in snowpack tests. As more snow builds over this layer, it could become touchy.Older snowpack weaknesses buried in the upper snowpack (Feb 4th and Jan 23 surface hoar/facet/sun crust layers) are still being tracked by professionals. There is some potential for triggering one of these deeper layers with a large trigger like an avalanche in motion, or from a thin-spot trigger point. The lower snowpack is generally well settled.

Regions covered