Cold temperatures are expected to prolong a poor bond between the old and new snow. Keep in mind that cold temperatures can also increase the consequences of an incident. Enjoy the winter wonderland in low consequence, wind-sheltered areas.
Since Friday, 25-40 cm of new snow has accumulated, forming a widespread storm slab problem that may remain reactive to human triggering. Strong south winds during the storm have likely built larger, more sensitive slabs in wind-drifted areas at upper elevations. Cold temperatures mean that the new snow could take more time than usual to bond with the previous snow surface.
Cold, Arctic air and north winds take the reins
Saturday night: Mostly cloudy, isolated flurries with trace accumulations, winds becoming north and decreasing to light, treeline low temperatures near -13 C, freezing level at sea level.
Sunday: Mix of sun and cloud, no new snow expected, light north winds, treeline high temperatures near -15 C, freezing level at sea level.
Monday: Mix of sun and cloud, no new snow expected, winds becoming northwest and increasing to moderate in the afternoon, treeline high temperatures near -13 C, freezing level at sea level.
Tuesday: Mainly clear, a trace of new snow possible, moderate north winds, treeline high temperatures near -12 C, freezing level at sea level.
On Friday, we received several reports of touchy conditions in the North Shore Mountains. The new snow was sliding easily on a rain crust on steep terrain features. Check out these MIN reports from near Hollyburn, Pump Peak, Brockton Point early and Brockton Point in the afternoon for great descriptions and photos of these conditions.
Since Friday, the mountains picked up another 25-40 cm of cold, light snow. Slab avalanches may remain sensitive to triggering where the new snow has been drifted by wind or where it remains poorly bonded to the old snow. Cold temperatures will likely delay how long it takes for the new snow to form a bond with previous surfaces, which include preserved powder and wind-packed snow at upper elevations and a rain crust near and below treeline.
Moderate to strong south winds have had an ample supply of light, cold snow to drift into reactive slabs. Winds are forecast to shift to the north and decrease to light, which may have the potential to create an unusual cross-loading or reverse-loading pattern in wind-exposed areas. Start simple and gather information as you go. Monitor for changing slab conditions as you move into wind-exposed terrain and assess the bond of the new and old snow interface. Seek out softer conditions in wind-sheltered areas.
In the north of the region, a concerning layer of facets (sugary snow) can be found down 100-200cm over a crust that formed in early December. This layer is slowly transitioning from stubborn to unreactive as the snow above stiffens and makes it harder to trigger. This problem is particularly hard to predict and tricky to manage. Get more details and photos in our forecaster blog.
Be sure to watch this week's snowpack summary video from North Shore Rescue.
