Skiers and snowboarders got a little good news and bad news this past week, as winter conditions returned after two weeks of warm and dry weather.
The good news is that the top layer of snow has bonded and Whistler Blackcomb has been able to open more terrain, and will be close to 100 per cent open by the end of the week. The bad news is that the underlying weak layer continues to pose a serious avalanche hazard in the backcountry, and that large slides are still possible.
"What happened is that we needed the temperatures to get cold again," said Doug MacFarlane, mountain manager for Whistler Blackcomb.
"We had the original instability in the snow pack and then suddenly temperatures went from winter to plus 10 and plus 14 at the peak during the warm spell, which created another hazard with the spring-like conditions. Basically the pendulum swung from one extreme to the other, with nothing in between."
Whistler Blackcomb stepped up its avalanche control work, trying to get steeper slopes to release at the weak layer. At the same time the upper layers of snow bonded well in the recent cold weather, allowing more areas to open.
In the last week or so, patrol has been able to open Lakeside Bowl, Spanky's Ladder, and the Blackcomb Glacier on Blackcomb - the latter by using avalanche debris from the far side of the Glacier area - and Whistler Bowl, West Bowl, Flute Bowl, Peak Chair and Symphony Chair on Whistler. They expect to open Peak to Creek by the end of the week with more snow coverage on the lower areas, and the Grand Finale exit from Whistler Bowl. Some double black areas are also closed.
All closed areas are designated beyond the ski area boundary, so you can ski or snowboard at your own risk. There are no patrol closed areas where you can lose your pass, other than the usual permanently closed areas.
"Next week it's looking good for the area with more storms in the forecast, and hopefully they all materialize," said MacFarlane.
Snowmaking is still underway on the ski-outs, and will likely continue into February.
"At this point we're just fattening things up in case there's an early spring, and we need an extra something in the bank account," said MacFarlane. "It's been an unusual year. We didn't get to make as much snow as we wanted to because of the weather, then we ran out of water, then it got too warm to make snow. It was always in our plan to make a lot of snow, but we might go a little longer this year into February."
While every little bit helps, MacFarlane is still urging people to be careful heading into the backcountry.
"It's sleeping," he said of the weak layer. "The instability is dormant right now, it's not gone. When we get a lot of new snow we could be faced with closures in some of the terrain we've opened until we get (the snowpack) to move again. If we get snow in small increments the hazard might not increase as quickly... but there are still areas that haven't gone (slid) yet down to the weak layer. Some areas have bridged and haven't released, while a lot of the bigger slopes have already gone. We've been recording what's gone and what hasn't so we'll have a reference."
Cam Campbell, a public avalanche forecaster for the South Coast Zone for the Canadian Avalanche Centre, is also urging caution.
"We had a lot of settlement (the past week), and that caused the slab to stiffen and essentially bridge over the weak layers at the base of the snowpack. That bridge is effectively holding the weight of skiers and snowmobiles," he said.
"We're also seeing that it's highly variable and unpredictable. Bridging is a poorly understood phenomenon, and we're still seeing avalanches trigged by light loads in steep or rocky areas where the bridge isn't as thick.
"And these avalanches are quite big, because the weak layer is so thick that it can propagate fractures over huge distances, and in some spots to two metres deep."
His advice to backcountry users is to understand that the hazard is not over, and that the snow pack remains unpredictable. The snow that fell this week and that's in the forecast could also create a new hazard.
"There are areas where we're seeing obvious wind loading and wind slabs that are likely to be weak," he said.
"The advice to anyone going into the backcountry is the same, to stick to simple, low angle and primarily forested terrain that isn't threatened from above. It may not be what people are chomping at the bit for, but steep, exposed alpine lines are not a good place to be unless you're absolutely certain - and with these conditions you just can't be absolutely certain."
The weak layer is the result of a deep freeze in early December, followed by light, dry snow. Heavy layers covered up and compressed that dry layer, which still has not bonded with the frozen layer below or the heavy snow on top and may continue to be an issue through to the end of the season. Slopes that have had avalanches, natural or man-made, are generally safer than slopes that have not moved.
Campbell says the hazard rating is going up for the coast and Whistler area through the weekend, and advised people to check the avalanche bulletin at www.avalanche.ca to get the latest forecast. As well, people in the Whistler area should check the avalanche advisory at www.whistlerblackcomb.com.
"It's moderate now, but you can see that the hazard is going up to high and considerable later in the week," said Campbell. "The conditions can change fast, and hazard rating can be updated overnight if avalanche forecasters observe anything unusual."
Fundraising dinner to benefit Avalanche Centre
The Canadian Avalanche Foundation, which raises funds for the Canadian Avalanche Centre, is holding a gala dinner and silent auction on Feb. 20 in the Roundhouse Lodge.
The evening is presented by foundation president and avalanche forecaster Chris Stethem, with guest speaker Hector MacKenzie presenting "Northern Avalanches and Polar Adventures."
MacKenzie has studied avalanches for more than 40 years, and has made expeditions to both poles to study avalanche activity.
Tickets to the dinner are $175 each, and $1,500 for a table of 10. The event is Mountain Evening Dress, so wear your best ski sweater or lederhosen.
For more information or tickets, visit www.avalanche.ca and click on the logo for the Canadian Avalanche Foundation.