With fresh wind loading in the alpine and another round of elevated winds with mild temperatures lined up for Sunday, slabs can be considered to be more sensitive to human triggering and natural avalanche activity to remain a possibility.
Thursday into Friday, wind values ranged from Moderate to Strong at upper elevations with some areas gusting into extreme. These winds redistributed 10 to 20cm of loose snow at upper elevations and have formed small, soft slabs isolated to immediate lees.
The lower snowpack is comprised of weak facets and depth hoar with the entire upper and middle of the snowpack forming an overlying slab 40 to 90cm thick. This weak basal layer is uniform across most of the forecasting region and has been responsible for most of the avalanche activity to date this season. Modest loading in the alpine and warming temperatures may have made these slabs a bit more sensitive to human triggering over the last few days. Choose smaller slopes and keep the slope angle modest to avoid triggering these high consequence slabs.
Only a few loose dry avalanches to sz 1.5 were seen out the alpine on Mt Cascade today however teams only went as far as the Sunshine backcountry. Both ski hills reported dealing with fresh soft cornices that would trigger small slabs 5-10 wide and 10-20cm deep. Lake Louise triggered a sz 1.5 slab on the Dec 17 layer in a previously uncontrolled area that stepped down to the Nov 16 layer in a few pockets.
10-20 cm of loose snow can be found on the surface including modest accumulations of new snow over the last few days at upper elevations. On Thursday and Friday, moderate to strong SW winds redistributed this loose snow in the alpine and formed fresh small, soft wind slabs in immediate lees with corresponding cornice development. Below 2000m warm temperatures have created moist snow: expect thin surface crusts as temperatures cool.
The December 17 persistent weak layer of facets is down 25-50 cm.
The November 16 deep persistent weak layer of facets and depth hoar is near the base of the snowpack (40 to 90cm deep) and continues to show failures with a sudden character in snowpack tests.
A profile from the Sunshine Backcountry today here.
Freezing levels will return to valley bottom Saturday night after another warm day. Isolated flurries will end overnight to allow for broken skies to start Sunday. Freezing levels should just reach valley bottom Sunday as south winds increase to 30-40km/h. Clouds will increase in the afternoon and allow for trace amounts of snow to accumulate overnight as freezing levels return to valley bottom.
