Avalanche forecast

Kootenay Boundary

Mar 5 – 6, 2022Avalanche Canada
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Avalanche danger

Mon
Tue
Alpine
2 · Moderate
Treeline
2 · Moderate
Below
1 · Low
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Highlights

A frozen crust in the upper snowpack is bad news. Travel conditions could be very challenging. If there is new snow on top of the crust, it could slide easily, and slide far. 

Clear skies will improve the view, but avalanches will be more likely on sunny slopes.

Avalanche problems

  • Persistent Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Unlikely - Possible
    Size
    2–3.5

    Persistent weak layers could be potential problems as the recent snow settles into a denser slab. A 1-5 cm thick crust that formed in early March is making it more difficult to affect these layers with the weight of a human or snowmobile. Use extra caution if this crust is not present, or is breaking down due to warming from the sun. 

    Weak layers from February (mostly crusts and surface hoar) are likely down around 60 cm and may become more reactive as the overlying snow has formed a thicker and more cohesive slab. Two weak layers of surface hoar from January are likely down around a meter and were primarily a concern in the east of the region on northerly aspects around treeline. 

    Avalanches that start in the recent snow have the potential to step down to these deeper layers. 

  • Storm Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Possible
    Size
    1–2

    Human triggering of storm slabs should remain on your radar. Thursday night's snow may slide easily on the underlying crust that has been reported as high as 2200 m.  

    Test the bond of new snow on smaller terrain features with low consequences as you travel through various elevation bands and aspects.

    If you don't find a crust on or near the surface, or if you easily break through the crust, it will be possible to trigger avalanches deeper in the recent storm snow. 

    Cornices have grown during the last system as well so give them a wide berth.

Confidence

High - We have a good understanding of the snowpack structure and confidence in the weather forecast

Weather Forecast

Friday Night: Mostly clear. No new snow expected. Light north wind. Cold air pooling in valley bottoms, making for a short-lived temperature inversion. Alpine low around -5 °C.

Saturday: Mostly Sunny. No new snow expected. Light north wind. Freezing level rising to 1500 m through the day. Alpine high around -3 °C.

Sunday: Sunny. No new snow expected. Light northeast ridgetop wind, trending to moderate in the high alpine. Freezing level at valley bottom overnight, rising to 1500 m through the day. 

Monday: Mostly cloudy. Moderate northwest ridgetop wind, trending to extreme in the high alpine. Freezing level at valley bottom overnight, rising to 1500 m through the day. 

Avalanche Summary

On Friday, south of Nelson, natural loose wet avalanches were reported up to size 1.5 in the afternoon on steep solar aspects. Also, east of Kelowna, a natural windslab avalanche and several explosive triggered windslabs were reported up to size 1.5 on east through south aspects around treeline. 

Additionally, east of Slocan (in the neighboring South Columbia region), a snowmobile triggered size 2 avalanche was reported, no other details at this time. 

On Thursday, south of Nelson, avalanche control with explosives triggered several small to large avalanches, failing below through the crust that formed on Wednesday.

On Wednesday, several natural and explosive triggered storm slabs up to size 2 were reported across the region. Also, a professional operation west of Trail reported a large natural loose wet avalanche below tree line that scoured to ground, and ran to the end of the path, 550 m long. 

Snowpack Summary

5-20 cm of new snow sits on a 1-5cm rain crust that goes as high as 2200 m in some parts of the region. There are a few great Mountain Information Network posts that describe the challenging backcountry travel conditions on Thursday due to this crust. 

Some places in the Kootenay Boundary have received over 60 mm of water over the course of the storm that started in the last few days of February. That has translated to about 20-50 cm (depending on elevation) of settled snow. This recent storm snow sits on a variety of hard surfaces, and feathery surface hoar crystals in some locations.

Weak layers from mid-February and late January made up of crusts and/or surface hoar crystals can be found around 60-70 cm deep. There are not a lot of recent avalanches on these layers, but they are still on the radar of operators in the area.

Terrain and Travel

  • A crust on the surface will help bind the snow together, but may make for tough travel conditions.
  • Closely monitor how the new snow is bonding to the crust.
  • Be alert to conditions that change with elevation.
  • Use small low consequence slopes to test the bond of the new snow.
  • Storm slabs in motion may step down to deeper layers resulting in large avalanches.

Regions covered