The recent snow has formed new slabs. It has also loaded weak layers that are at a prime depth for riders to trigger them.
Winds have shifted to the north and they may produce new wind slabs on slopes that don't typically hold them. The most suspect terrain features would be steep slopes immediately adjacent to ridges. The recent snow may also be reactive to human traffic in sheltered terrain features.
A couple problematic layers exist around 50 to 100 cm deep, including weak layers of surface hoar and faceted grains above a hard melt-freeze crust. The possibility exists that humans could trigger this layer where it exists in the mountains.
MONDAY NIGHT: Clear skies, 40 km/h north wind, alpine temperature -11 C.
TUESDAY: Clear skies, 10 to 30 km/h north wind, alpine temperature -11 C.
WEDNESDAY: Mix of sun and cloud, 10 to 20 km/h southwest wind, alpine temperature -2 C, above-freezing layer forming around 2000 m.
THURSDAY: Clear skies, 20 km/h south wind, alpine temperature 2 C, freezing level 2200 m.
Many wind and storm slab avalanches were triggered naturally, by riders, and explosives on Sunday. They were generally large (size 2) and occurred at all elevation bands.
The latest confirmed avalanche on the weak layers described in the snowpack summary was December 19, where a few large avalanches were triggered by riders and explosives. They occurred on northerly aspect in alpine terrain (2100 m) and were generally 30 to 50 cm deep.
Around 20 cm of snow fell on Monday with strong northerly wind. Wind slabs may linger at treeline and alpine elevations on all aspects due to wind starting from the south and shifting to the north. In sheltered terrain, numerous storm snow interfaces may be found in the top 50 cm of the snowpack, which may take a couple of days to bond.
Two concerning weak layers are present in the snowpack. The shallower layer, being around 50 to 80 cm deep, includes feathery surface hoar crystals. There is uncertainty in the distribution of this layer, but the most likely place to find it would be in terrain features sheltered from the wind around treeline and lower alpine elevations. The more widespread weak layer includes sugary faceted grains that overlies a hard melt-freeze crust. This layer is generally found around 50 to 100 cm deep and is widespread up to around 2000 to 2200 m.
The remainder of the snowpack is well-settled.
