As of Wednesday, Nov. 21
Below Treeline: below threshold
Winter looks as though it has finally arrived and is
going to stay. The bulk of the snow cover fell with the Nov 11/12 storm. High
alpine areas have about 150 to 200 cm of snow and the base at treeline is about
100 cm. As is the norm at this time of the year, there are lots of exposed or
not so exposed hazards. Take it easy if you are planning to head into the
backcountry — don’t end your season during the first week!
We have seen little in the way of avalanche activity
during the past few days. Minimal explosive testing carried out on Nov. 17 did,
size 2.5 avalanches that ran in start zones at 2,125 metres on north facing
aspects. The crown lines went from about 40 cm to a maximum of 160 cm. Two
distinct steps were visible in the slab and it appeared that they were
triggered in the rocks and pulled into the fat part of the slope. More
extensive explosive testing was carried out again Nov. 18 after significant
overnight cooling, and we saw only small surface slabs involving the overnight
Snowpack: A fracture line profile at one of the previously mentioned avalanche sites indicated that the slab failed at the bottom of a layer of mixed/faceted crystals sandwiched between two crusts. The upper crust is about 8 cm thick while the lower one goes down 40 cm to the summer firn. The overlying slab varied in density from 1F to pencil. Depending on elevation, you will find a different combination of crusts in the lower snowpack. Above about 2,050 metres there are the two, while at treeline elevations there is only one going to the ground. At 1,650 metres there is no crust on the ground and two thin lenses in the upper 30 cm. A temperature gradient is developing in the upper layers, and it can be expected to steepen with the forecast cool clear days. Surface hoar to 10 mm has formed during the clear overnight hours. Travel with extra caution if you are on big slopes. It appears that rocky areas may be good trigger points for a deeper release, but then again, maybe the cooler temperatures have tightened up the snowpack for now.
A ridge of high pressure is forecast to bring mainly sunny skies through the
remainder of the week. Temperatures are expected to begin warming by Friday.
Remember that there are still many exposed early season hazards so take it easy out there. Watch for winch cats and snowmobile traffic if you re-enter the ski area after operating hours. Call 604-938-7676 or surf to avalanche.ca or whistlerblackcomb.com for more information.
– Whistler Mtn. Snow Safety