Buried surface hoar may become touchy as snow accumulates. Approach steep open slopes at treeline and below with caution. Watch for signs of instability & consider conservative terrain as a way to manage uncertainty.
Wind slab will continue to form in exposed terrain.
Wind slabs may continue to build with strong westerly winds and new snow on Friday. Expect reactivity where they overly a smooth crust, or a weak surface hoar layer in sheltered terrain features.
Look for wind loading in unusual places, as direction has varied from northwest to southwest. Stronger wind speeds may also load mid slope features.
Fresh snow sits builds over a large and sensitive surface hoar layer, which sits on a crust on south facing slopes. Treat open slopes at treeline and below with caution - they may be more reactive and produce larger avalanches than you expect. Shooting cracks or whumpfing are clear signs to keep terrain choice conservative.
Light snowfall is forecast for Friday. Temperatures rise and skies clear for the weekend.
THURSDAY NIGHT: Mainly cloudy. Moderate westerly winds. Chance of flurries. Freezing level valley bottom.
FRIDAY: Cloudy with 10-15 cm of low density snow and strong southwest winds. Alpine high of -7. Freezing levels around 500 m.
SATURDAY: Strong west/northwest winds . Cloudy with a chance of flurries. Alpine high of -3, as freezing levels rise to 1000 m over the day.
SUNDAY: Clearing skies, no precipitation expected. Alpine high of 0, with freezing levels rising to 2000 m with an inversion possible. Moderate westerly winds.
Human triggered slabs to size 2 have been reported each day this week, up to size 2 in wind loaded terrain features. Activity has mainly been at higher elevations, on north and east facing slopes.
Several size 1 loose dry avalanches were also reported, mostly in steep terrain features.
At lower elevations up to 35cm of storm snow sits over a melt freeze crust. In sheltered terrain a widespread layer of large surface hoar crystals sits immediately above the crust, sensitive to human triggers.
At higher elevations the storm snow is being redistributed by moderate to strong westerly winds. A thin melt freeze crust extends into the alpine on solar aspects. This crust may sit on the surface in exposed terrain, or below wind deposited snow in sheltered features increasing reactivity.
The upper snowpack then consists of several crusts and surface hoar layers, 30-70 cm deep. Recent reactivity has appeared limited to the storm snow and most recent surface hoar.
The early December crust/facet persistent weak layer is buried down 100-200 cm and has been responsible for significant avalanche activity in this region. The layer is now considered dormant, but still remains a concern and we will continue to track it in the snowpack. See the most recent forecaster blog on how to manage this layer, as it will come into play again later this season.
