Mt. Field, Mt. Stephen, and Mt. Dennis avalanche closure zones are CLOSED on Friday, January 17th.
New windslab development in the alpine down into treeline and possibly below with strong to extreme SW wind on Thursday.
Strong to extreme winds with light flurries created fresh reactive windslabs 10-30 cm thick in alpine lees. Winds were observed to be transporting snow below treeline. It's possible windslabs exist in isolated slopes that are open and exposed to wind below treeline.
The snowpack is generally deeper and, thus, stronger in the Little Yoho subregion than in most of the BYK forecast region. However, thin snowpack areas, such as windward and exposed terrain, will have weak basal facets at the base of the snowpack.
Thursday morning, several size 2 wind-triggered slabs and loose dry avalanches were observed in Little Yoho on Mt. Stephen and Mount Field. Avalanche control on Mt Bosworth produced one size 2.5 sliding on the deep persistent layer.
10 cm new today with strong to extreme SW - W winds created new wind slabs at all elevations in terrain exposed to the wind. The upper pack may have a thin crust under the new snow on solar aspects and a surface hoar/facet interface under last week's snow, but no avalanches observed on this layer yet. The mid-pack is generally strong; however, a weak facet layer can be found near the ground in shallow snowpack areas. At treeline, average snowpack depth ranges from 120 to 150 cm.
On Friday, we will see cooling temperatures (-14C) and easing winds as arctic air moves in for the weekend. Saturday temperatures will be in the -20C range with sunny skies and light NW wind
