Kootenay Boundary

Poor - Timing, track, or intensity of incoming weather is uncertain

The next wave of snow is forecast to move into the interior from the coast on Saturday afternoon. The freezing level should rise quickly up to about 2000 metres late in the day Saturday, descend a bit overnight into Sunday and then rise again Sunday to about 2000 metres. This storm is forecast to bring strong southwest winds and moderate to heavy precipitation from Saturday afternoon until late in the day Sunday. Monday should be much drier and cooler as high pressure moves in behind the storm. I think that this storm will probably cause another cycle of natural avalanches, and continue to cause conditions that are very likely for human triggering.

Several natural avalanches have been reported from the southern part of the region. These range in size anywhere from size 1.0-2.0 between 1900-2000m on southeast aspects. Avalanche control work also produced avalanches up to size 2.5 on southeast-southwest aspects between 1900-2100m. This information is from a portion of the region and avalanche activity may differ with size, aspect, and elevation around your local mountains.

I have added a bit of information from the Selkirks to the North of this region. We are not getting much information from the Kootenay-Boundary, but I suspect that there is a great deal of variability in this region as well. The next storm is forecast to get pushed along the US border, which sometimes means greater than forecast snow amounts in this region. Take a minute to read about what we know happened in the Selkirks. I would not be surprised to hear of similar things happening in this region. Until we know otherwise lets assume that the recent heavy loading has caused storm slabs and or deep instabilities that can be triggered by humans.Generally we have about 150 cms in the alpine, and treeline has been showing some variability between 50 -150 cms. There are locations in the alpine that have 200 cms plus already. The freezing level went up to about 1900 metres on Wednesday and caused some pretty rapid settlement, followed by below freezing temperatures that have re-frozen the snow pack up to about treeline elevations. The wind has come from the southwest during the last storm, and then strong from the northeast immediately following the storm. Yesterday the wind was strong in the alpine from the east-southeast. We were feeling pretty sure that there was a major avalanche cycle going on in the alpine, that we thought was probably failing on the buried surface hoar layer that has been reported to be down about a metre. Today we received new information from the Selkirks south of Revelstoke that there was indeed a major avalanche cycle up to size 3.5 during the last storm, but it appears that most of the avalanches were sliding on a layer that is near the ground; perhaps a rain crust from October. The slides may have started on the surface hoar layer and then stepped down to the crust. We hope to get some more information soon, as operators start getting out into the field. There is probably a lull in activity today (Friday), but I am hesitant to bring down danger ratings with the limited information that we have. The next storm is forecast for Saturday, and it looks like it is going to come in warm again, maybe up to 2000 metres. I think the "take home" advice from recent activity is that you should be very suspicious of any slopes in the alpine that have not recently avalanched. If there is a crust of some type down low near the ground, you should be watching out for areas that might re-load with the next storm. Due to the variability of the amounts of snow in different drainages, I think that the absence of recent avalanche activity in an area would concern me as well. These are difficult early season conditions to evaluate. I recommend being very conservative this weekend. It is going to take a few days at least before we see any improvement. Let me know what you think! [email protected]