Regions
Kootenay Boundary.
There is quite a bit of variation in snowfall amounts across the region. Avalanche danger could be higher than forecast in areas where more than 25cm of settling snow is sitting above the layer of recently buried surface hoar.
Confidence
Moderate - Forecast snowfall amounts are uncertain
Weather Forecast
Unfortunately Thursday is expected to bring the last precipitation for a while as we start a cooling and clearing trend. Up to 10cm of new snow could fall on Thursday with only isolated flurries currently forecast for Friday. Saturday should be dry. Winds will be light from the North on Thursday becoming westerly by Saturday. A descending artic front will keep temperatures cool with freezing levels falling from 1000m on Thursday back close to valley bottom by the weekend.
Avalanche Summary
Reports suggest that the layer of buried surface hoar is starting to wake up especially in the south west of the region where overlying snow load above is greatest. Small natural avalanche were reported in steep open features at treeline on Tuesday.
Snowpack Summary
Recent snowfall amounts have been highly variable across the region. Up to 30cm of new snow has fallen around Rossland while Nelson has received about 15cm with less than 10cm for Kootenay Pass. Warm temperatures and moderate southerly winds on Tuesday have encouraged the formation of soft slabs in wind loaded features especially in the Southwest of the region. The new snow is covering a widespread layer of surface hoar. These weak crystals sit above a melt-freeze crust on solar aspects, old wind slabs in exposed higher elevation terrain and loose facets in sheltered areas. Between 40 and 60 cm below the surface, the mid-December interface can be found which consists of surface hoar or a sun crust. The early December rain crust can be found about 20 cm below that, up to an elevation of 1400m. Both of these layers are thought to be gaining strength and are no longer reacting to snowpack tests except in isolated locations. The snowpack below these layers is generally strong and well-settled.
Problems
Storm Slabs
Storm Slab avalanches are the release of a cohesive layer (a slab) of new snow that breaks within new snow or on the old snow surface. Storm-slabs typically last between a few hours and few days (following snowfall). Storm-slabs that form over a persistent weak layer (surface hoar, depth hoar, or near-surface facets) may be termed Persistent Slabs or may develop into Persistent Slabs.