Avalanche forecast

Kootenay Boundary

Mar 5 – 6, 2012Avalanche Canada
View on map
Archived · expired 15 years ago

Avalanche danger

Wed
Thu
Alpine
3 · Considerable
Treeline
3 · Considerable
Below
3 · Considerable
Open full map

Avalanche problems

  • Wind Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Likely
    Size
    2–4
    Generally lurking below ridgecrests, behind terrain breaks, and in gullies. Wind slabs are touchy and continued strong winds over the forecast period may overload weaknesses.

  • Persistent Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Possible - Likely
    Size
    2–6
    Persistently weak buried surface hoar demands continued diligence and conservative decisions. The potential for remote triggering, step down avalanches, and wide propagations, makes this weakness particularly tricky to predict.

  • Storm Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Likely - Very Likely
    Size
    1–4
    Formally touchy weaknesses within the recent storm snow will be less tender Tuesday with the forecasted cooler temperatures, but will still be a concern on both convex & unsupported features.

Confidence

Fair - Freezing levels are uncertain on Thursday

Weather Forecast

The Kootenay Boundary should see 10cm during the day Monday and another 5 cm Monday night. Tuesday starts out clear & cold accompanied by light northwest winds. The freezing level climbs to 800m Tuesday, falling back to the surface overnight. On Wednesday warm air floods the region, as a result freezing levels climb to 2000m. Winds should be moderate out of the W at treeline Wednesday, Strong out of the NW at ridgetop. Thursday looks to be the warmest day with the freezing level climbing to 2200m in the afternoon.

Avalanche Summary

On Sunday the wind, warmth and new snow came together to produce a natural avalanche cycle which averaged size 2, but did produce one size 3. It sounds like a few avalanches stepped down to the Mid-Feb Surface Hoar. The majority of the action involved more superficial soft slab avalanches with crowns 5 - 10 cm in depth. The Bonningtons harbor a weaker snow structure than most of the region; On Sunday cornice fall triggered a size 3 avalanche in low angle terrain (25 - 30 degrees) This avalanche was on a N-NE facing slope, the crown line is reported to be 80 - 120 cm in depth. Conditions Monday are very similar to Sunday and I expect natural avalanche activity to continue.

Snowpack Summary

Sunday & Monday were warm windy days in the mountains. Stagleap Wx station at 2140m reached -0.9 C Sunday at 11:00. This warmth has changed the character of the supper snowpack, allowing it to settle & gain strength. Ski quality has suffered a bit, but, in the long run this will help to heal our snowpack. In the short term there are two problem layers to watch; A. The Feb. 29 interface which consists of surface hoar on shady aspects and a thin sun crust on south aspects, down around 30cm. B. Surface hoar buried mid-February, which is now down 70-120cm and still giving sudden snowpack test results. 10+ cm is forecasted for Monday afternoon which will hide the cohesive slab beneath.We often think about cold temperatures “locking things up.” Tuesday dawns cold & cloudy, but 10+ cm's from Monday will insulate 100cm of very warm snow that rests on the mid Feb SH. With this structure in place, we need to give the snowpack some extra time to adjust. Continue to stay conservative in your terrain selection Tuesday and be sure to factor the surface hoar problem into your decision making as you travel in the mountains Tuesday. The surface hoar problem is far from over.

Regions covered