New snow and wind will keep our wind slab problem alive for Wednesday. Meanwhile, the snowpack will be adjusting to warming temperatures. The effects of this warming are uncertain so it's a good time to build extra safety margins into your terrain selection.
Light new snow amounts feeding into southwest winds will continue to deposit new snow into wind slabs in lee areas in the alpine and treeline as well as in exposed areas below treeline. A pattern of rising temperatures will promote slab formation and slab reactivity on Wednesday.
Tuesday night: Cloudy with flurries bringing 5-10 cm of new snow. Moderate to strong southwest winds.
Wednesday: Mainly cloudy with isolated flurries and a trace of new snow, increasing overnight. Moderate to strong southwest winds easing over the day. Treeline high temperatures around -4 with freezing levels to 1300 metres.
Thursday: Clearing, with 10-20 cm of new snow from the overnight period. Light west or northwest winds. Treeline high temperatures around -3.
Friday: Becoming cloudy with isolated flurries and a trace of new snow. Strong southwest winds becoming extreme by evening. Treeline high temperatures around -2 with freezing levels rising to 1100-1400 metres by evening.
Reports from Monday included several more observations or recent natural wind slab releases with sizes ranging from 1-2 (small to large). North aspects were highlighted.
Our North Rockies field team got out to Hasler on Sunday, and they saw a small avalanche on a wind loaded slope just below a ridgeline, and saw other signs of instability. Check out their MIN report here for more details and a report on snow conditions.
There are very few reporting operations in this region, so remember that a lack of observed avalanches does not necessarily mean that there is a lack of avalanche activity. If you are getting out, please post your observations to the Mountain Information Network!
Up to 15 cm of new snow is expected by Wednesday morning, adding to 10-35 cm of snow the region has received since Sunday. In exposed areas at treeline and above, southwest winds are expected to continue redepositing this snow into wind slabs in lee areas.
Our recent snow collectively overlies a previously wind-effected surface comprised of old hard wind slabs, sastrugi, and areas stripped back to the ground or old crusts. Snow at this interface was significantly weakened during the cold snap, which means the bond here remains in question. This is especially important as forecast new snow and warming make their way into the region.
A crust that was formed at treeline elevations and below in early December has been reported in parts of this region. It can be found down 50-100 cm. There have been no recent reports of avalanches on this layer. Although this layer is now considered dormant in the region, a large amount of new snow or warming temperatures have the potential to wake it up, and larger avalanches in surface layers or natural cornice falls may have potential to step down to this layer in isolated areas.
The base of the snowpack is composed of crusts and weak faceted grains, particularly in thin snowpack areas east of the divide.
